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Geotourism Highlights of Gotland

Geotourism Highlights of Gotland

GEOTOURISM HIGHLIGHTS OF

NGO GEOGUIDE DEPARTMENT OF EARTH SCIENCES, UNIVERSITY GOTLANDS MUSEUM

GEOTOURISM HIGHLIGHTS OF GOTLAND

Tallinn, 2010 Geotourism highlights of Gotland. NGO GEOGuide Baltoscandia. , 2010. ISBN 978-9985-9973-4-5

Compiled by: Sara Eliason Michael G. Bassett Sebastian Willman

Proof-reading: Graham E. Budd Layout: Heikki Bauert Photos & Illustrations: Heikki Bauert, if not otherwise stated Cover photo: Sea stacks at Gamlahamn, western Fårö

© NGO GEOGuide Baltoscandia ©

E-mail: [email protected]

Acknowledgements: Gotlands Museum, National Museum of Wales, Raymond Hejdström, Lars Holmer, Paula Knapman, Jan Olsson, Henrik Reintz, Michael Streng, Hanne Ödin, Gun Westholm

EUROPEAN UNION EUROPEAN REGIONAL DEVELOPMENT FUND INVESTING IN YOUR FUTURE

Release of this book was co-financed by European Regional Development Fund, Environmental Investment Centre, and NGO GEOGUIDE BALTOSCANDIA. It was accomplished within the framework of the CENTRAL BALTIC INTERREG IVA Programme 2007-2013. Disclaimer: The publication reflects the authors views and the Managing Authority cannot be held liable for the information published by the project partners. CONTENTS

Introduction ...... 5 Geological History of the ...... 6 The Bedrock and the Geology of Gotland ...... 11 The Sedimentary Rocks of Gotland ...... 13 Gotland ...... 22 Landscapes of Gotland today ...... 27 The Baltic Sea and the Sea Coast ...... 30 The Inland ...... 35 History and Cultural Heritage of Gotland ...... 37 Industrial History of Gotland ...... 40 Geotourism Destinations ...... 42 Surroundings ...... 42 Högklint and Rövar Liljas Håla ...... 42 Snäckgärdsbaden and Korpklint ...... 44 Lummelundsbruk and Cave ...... 46 Northwestern Coast ...... 47 ...... 47 ...... 50 Bläse Limeworks Museum ...... 54 Fårö ...... 55 Digerhuvud ...... 55 Avanäset ...... 56 Langhammarshammar ...... 58 Northeastern Coast ...... 60 Lergrav ...... 60 Kyllaj ...... 61 St Olofsholm ...... 65 Northern Inland ...... 66 Tingstäde – area ...... 66 Eastern Coast ...... 70 Gothemhammar ...... 70 Grogarnshuvud ...... 71 Kuppen and Snabben ...... 73 Southeastern and Southern Coast ...... 74 Uggarderojr ...... 74 Holmhällar ...... 75 Husrygg and ...... 78 Kettelvik ...... 80 Kettelvik Sandstone Museum ...... 81 Stora Karlsö and Lilla Karlsö ...... 84

Introduction Apart from these rich human cultural attractions, Gotland has many rich natural features that make it The island of Gotland, situated in the centre of the Baltic Sea on the eastern periphery of , is the different from other of Sweden, related espe- largest of the Baltoscandian islands, with an area of cially to the bedrock that occupies much 2994 km2, compared with Öland (1347 km2), Saare- of the island. The rich flora, noted mainly for its rare maa (, 2673 km2) and (, orchids, the sedge fens and flush fens, the rocky lime- 588 km2). There are only 57 600 inhabitants of stone ground, the magnificent coastal and inland Gotland, but about 800 000 visitors come every year, scenery, and the remarkable sea stacks () mostly as tourists in the summertime. are all features of the geological heritage. They owe their origin to the fact that the rocks of Gotland were Gotland is renowned for its beautiful scenery, espe- formed as sediments in a warm, shallow tropical cially along the coast where the wonderful sandy sea more than 400 million years ago. Human liveli- beaches attract people who want to swim and sun- bathe. There is also a rich cultural heritage, with hood derived from farming, forestry, cement produc- numerous ancient monuments and 92 impressive tion and the stone industry has been governed by churches throughout the island. The largest , the prevailing types of bedrock and soil. The Visby Visby, was a prominent trading town of the Hanseatic town wall and numerous churches mentioned above League in the 13th and 14th centuries, and this would not have existed without the local supplies of importance is reflected in its rich architectural herit- building materials. Even the renowned natural light age. The magnificent town wall and some 200 well of Gotland, which has inspired so many artists, is preserved medieval buildings of Visby are particular a result of the interaction between the sea and the attractions. beautiful grey .

Geotourism highlights of Gotland 5 But the bedrock also has another special aspect. It (Gotland and Öland) represent the northwestern mar- tells the story of life on earth long before humans gin of the overlying layers. appeared, and records changes of climate and envi- At the beginning of the Cambrian Period some 543 ronments over the course of millions of years. The million years ago, the , European study of fossils increases our knowledge of how ani- and some other areas of central and northern mals and plants have developed through time, and formed its own continental mass commonly known how all these factors have been affected by large as Baltica. The border ran through northern scale geological processes. and , across Russia, down to the northern part Gotland plays a prominent role internationally in our of the Black Sea and then north through the present understanding of geological processes. The island has Ural Mountains. The Baltic Sea region was a depres- some of the world’s best preserved shallow sea sedi- sion in the continental crystalline basement. The land ments and richest associations from its period of of Baltica had been exposed above sea level for a formation and development. The bedrock sequence long time, and had experienced a long period of ero- is essentially uninterrupted through its thickness sion that gave rise to a low-lying peneplaned surface. of close to 450 metres, recording some 10 million As the Cambrian commenced, Scandinivia and the years of the evolution of life on earth. Considerable Baltic Sea basin began to be flooded, starting from painstaking research has been undertaken into the the south. From the Cambrian up to the end of the description and interpretation of these sediments and Silurian period, a shallow sea lay here, with subse- their fossils, from as far back as 1741 when Linnaeus quent variations in land borders and depth. During spent just over one month on the island in June and these 135 million years Baltica gradually moved from July of that year and later described some fossils and a position far down in the north- geological features in various publications. Detailed wards towards the equator. mapping of the geology of Gotland was carried out as The climate that prevailed at the different latitudes early as the first half of the 20th century, and over 600 Baltica passed through on its long journey northwards publications have been produced by researchers from are reflected in the sediments that were almost con- all over the world since 1970 alone. tinuously deposited on the sea floor, and are now pre- served in widespread areas of and the Geological History of the Baltic Sea Baltic Sea Region. At certain times, the shallow sea Region stretched well up what is known today as the Scan- If you picture a map of the Baltic without any of the dinavian peninsular. The oldest Cambrian sediments water in the Baltic Sea, and instead include the sea consist of fairly pure, well-sorted sandstones. They bottom in a geological map of the region, the posi- comprise remains of the disintegrated land surface tion and age of Gotland and the other Baltic islands that has been washed and sorted by waves and cur- will be more clearly understood. The northern Baltic rents in the shallow cold water, so that sand grains of Sea islands (Åland, Swedish and Finnish archipelago) the hard mineral quartz are almost all that remain. belong to the crystalline basement whilst the Esto- All organic elements have been consumed in the nian ( and ) and Swedish islands oxygen-rich water. Large numbers of trace fossils of

6 Fostering Geotourism on the Central Baltic Islands Geological Time Scale

IUGS ICS Geological Time Scale 2004 (www.stratigraphy.org)

EONOTHEM/EON ERATHEM/ERA SYSTEM/PERIOD SERIES/EPOCH Age Ma 0,00 Holocene QUATERNARY 0,0115 Pleistocene 1,806 Pliocene NEOGENE 5,332 CENOZOIC Miocene 23,03 Oligocene 33,9 ± 0,1 PALEOGENE Eocene 55,8 ± 0,2 Paleocene 65,5 ± 0,3 Upper Cretaceous CRETACEOUS 99,6 ± 0,9 Lower Cretaceous 145,5 ± 4,0 Upper Jurassic 161,2 ± 4,0 JURASSIC Middle Jurassic MESOZOIC 175,6 ± 2,0 Lower Jurassic 199,6 ± 0,6 Upper Triassic 228,0 ± 2,0 TRIASSIC Middle Triassic 245,0 ± 1,5 Lower Triassic 251,0 ± 0,4 Lopingian 260,4 ± 0,7 PERMIAN Guadalupian PHANEROZOIC 270,6 ± 0,7 Cisuralian 299,0 ± 0,8 Pennsylvanian CARBONIFEROUS 318,1 ± 1,3 Mississipian 359,2 ± 2,5 Upper Devonian 385,3 ± 2,6 DEVONIAN Middle Devonian 397,5 ± 2,7 Lower Devonian 416,0 ± 2,8 PALEOZOIC Pridoli 418,7 ± 2,7 Ludlow SILURIAN 422,9 ± 2,5 Wenlock 428,2 ± 2,3 Llandovery 443,7 ± 1,5 Upper Ordoviciam 460,9 ± 1,6 Middle Ordovician 471,8 ± 1,6 Lower Ordovician 488,3±1,7 Furongian 501,0±2,0 CAMBRIAN Middle Cambrian 513,0±2,0 Lower Cambrian 542,0±1,0 EDIACARAN 630 NEOPROTEROZOIC CRYOGENIAN 850 TONIAN 1000 STENIAN 1200 PROTEROZOIC MESOPROTEROZOIC ECTASIAN 1400 CALYMMIAN 1600 STATHERIAN 1800 OROSIRIAN PALEOPROTEROZOIC 2050 RHYACIAN 2300 SIDERIAN 2500 NEOARCHEAN 2800 ARCHEAN MESOARCHEAN 3200 PALEOARCHEAN 3600 EOARCHEAN ~4500 burrowing tracks left by organisms like worms, indi- clay sedimentation continued throughout the period, cate abundant former life, though remains of shells while further north and east, in the shallower regions are rare. At the beginning of the Cambrian, Baltica of the sea, lime sedimentation occurred, indicating a was probably on the 60 – 70 degree southern parallel, warmer climate. This orthoceratite limestone (named where it was then (and still is) cold and windy. after the fossil shells of the cephalopods contained Gradually Baltica moved northwards and the sea within it), which can be found for example on Öland level continued to rise. The sediment from the mid- and Hiiumaa islands, is red to light grey in colour and and latest parts of the Cambrian has now consoli- rich in fossil shells, such as those of trilobites, cepha- dated to dark shale. Clay shale is the type of rock lopods and brachiopods. It was in the next period, the once deposited as a clayey mud in very calm, usually Silurian, that formations first became common in deeper water beyond the reach of waves and currents. the shallow coastal areas, indicating a more tropical The upper Cambrian so-called alum shale is black climate. owing to a high content of organic material (carbon- During the Silurian period, beginning 444 million ized disintegrated remains of animals and plants) and years ago and ending 416 million years ago, Baltica the iron-rich mineral pyrite. The oxygen deficiency was at, or just south of the Equator. Approaching on the sea bed, just as on the present-day Baltic Sea from the west was Laurentia, consisting of present floor, meant that the decomposition of the organisms’ day and Greenland. During the Sil- organic parts was only partial; and few animals could urian period the two finally converged. live on the sea floor. Therefore the remains of ani- The enormous force pressed together and crumpled mals such as the freely-swimming trilobites that accu- up the thick layers of sediment that had been depos- mulated, have been well preserved. The alum shales ited over a long period of time in the deep sea trench contain quite a lot of bituminous calcium in the form that had formed along the western edge of Baltica, of black, disc-shaped nodules, known as anthraco- when the sea floor was subducted under present day nite. The Cambrian strata are exposed in a narrow . The Caledonian convergence boundary that belt along the sea bottom and crop out in, for exam- we can see today in the central Scandinavian moun- ple, Skåne, on Bornholm, in the Kalmarsund, and in tain range (part of the Caledonian mountain chain) northern Estonia. emerged. South of Baltica and Laurentia lay the enor- The deposition of the black clay sediments contin- mous Gondwanaland, consisting of , South ued into the next period, the Ordovician, although America, Antarctica, , Madagascar, India and the sediment became lighter in colour. In Skåne the New .

Sweden Estonia A B Öland Gotland Hiiumaa

8 Fostering Geotourism on the Central Baltic Islands Finland

Sweden B

BALTIC SEA BEDROCK MAP

Quaternary

Cretaceous Estonia Jurassic Hiiu- maa Triassic

Permian

Carboniferous Saaremaa

Devonian

Silurian

Ordovician

Cambrian Undifferentiated Palaeozoic sedimentary rocks sandstone (1,35 Ga) Gotland

Rapakivi granite (1,6 Ga) Precambrian crystalline and metamorphic rocks

Öland 0 50 100 km

A

Lithuania

Russia Poland

Cross section of the rocks in the Baltic Sea area showing the similarities between Gotland and Saaremaa (left page). Distri- bution of rocks of varying ages in the Baltic Sea area (adapted from Ahlberg 1986, Swedish Geological Survey, R&M 47).

Geotourism highlights of Gotland 9 living on the bottom (ben- 425 Ma land ocean shallow shelf reefs thic), and for free swim- deep shelf volcanoes Kara ming ones (nektonic), as well as for the growth of Ægir algae. Organic reefs simi- lar to today’s reefs were periodically formed

Equator by sessile animals with calcareous skeletons. L A U R U S S I A Enormous amounts of Finland fragmented shells piled Estonia up on the sea beds around Sweden Gotland the reefs, and these even- tually consolidated into stratified limestone. At other times large amounts Perunica of clay sediment were deposited. These were RHEIC OCEAN combined with calcare- Avalonia ous material and formed 30oS thick, fossil-rich marlstone layers. Further away from Palaeogeography of eastern Laurussia in the mid-Silurian – the coast, in deeper and calmer water, almost pure Wenlock, 425 Ma (adapted from Cocks & Torsvik 2005). clay was deposited. This has now been transformed During the Silurian Period, the climate at the equator into light clay shale, which can be seen in Skåne, for was warm, just like today. The Baltic Sea Region and example. southern Scandinavia were covered by a shallow sea, Even in Skåne, reef-like calcareous knolls were and land lay in the north and the west. The absence formed at the end of the Silurian Period, indicating a of a vegetation cover and the tropical climate meant regression (the retreat of the sea). The very youngest that the land surface was subjected to intense weath- Silurian layers there consist of red sandstone, sedi- ering. Rain water fl ushed clay via rivers out to sea, ment that bears witness partly to an environment very where the small clay particles were held in suspen- close to land, possibly even continental, and partly to sion until the water fl ow had slowed. Near land – the fact that the buckling of the Caledonian moun- where Gotland’s bedrock was just being formed, for tains had taken place and that this newly-born moun- example – the shallow sea beds were rich in oxy- tain range had already been subjected to weather- gen, and sunlight could reach the seafl oor, provid- ing. Sand was also deposited in the Gotland region ing favourable conditions both for myriads of animals towards the end of the Silurian period.

10 Fostering Geotourism on the Central Baltic Islands At the beginning of the next period – the After millions of years of sediment accumulation, the Devonian – the entire area emerged above sea level, deposits were compressed by their own weight and where it probably remained even during the two sub- gradually consolidated to the rock that today forms sequent periods – the Carboniferous and Permian. Gotland’s bedrock. Normally only the topmost layer There are no sediments from these periods in Scan- (the youngest layer), would be exposed, but since all dinavia, but in southeastern Baltic Sea, as well as in the strata dip about 2 degrees southeastwards, and southern Estonia, Latvia and Lithuania there are some erosion, mainly by the inland ice has scoured away continental sandstones, mostly of Devonian age. Ele- much of the sediment at an oblique angle to the vation above sea level was probably caused by the dip of the strata, each layer protrudes and is more sinking of the oceanic ridges in the spreading centres or less accessible, from the oldest in the north west, of the oceans, and thus of the sea level, due to the towards the increasingly younger layers in the south interruption of tectonic movement following the con- east of Gotland. This largely uninterrupted fossilifer- tinental convergence. When plates move swiftly, on ous sequence of layers reflects the development of the other hand, magma pushes up the ocean floors at the earth and of life spanning some 10 million years. the spreading centres, causing them to rise. Gotland can be very roughly divided into three lime- At the beginning of the Silurian period, there is lit- stone areas, with marlstone areas in between. Lime- tle evidence for extensive land life. The sea, however, stone, which is harder and thus less prone to erosion, contained abundant vegetation and animals. Every forms the higher (30 – 80 metres above sea level) main group of animals existing today was already rep- areas in the north, in the central region of the island resented at that time. Some time during the Silurian and in the very south. A closer look at the stratigraphy Period, plants started colonising the land, and during on Gotland provides a more complicated picture, dif- the next period, certain fish developed the ability to ficult to interpret. At one and the same point in time move onto the land. there were obviously different depositional environ- ments, depending on the depth of water, reef forma- The Silurian Bedrock and tion, rate of sedimentation, etc, within the region of the Geology of Gotland Gotland, which is reflected in the fact that depos- its of equal age can differ in appearance and fossil The exposed bedrock of Gotland consists of reef content. Similarly, deposits at different levels in the limestone, stratified limestone, marlstone and a lesser stratigraphic column, and which differ chronologi- expanse of sandstone, as well as finer-grained silt. The cally by several million years, can be largely identi- strata, attaining an impressive thickness of 500 m, cal in appearance as the depositional environment were deposited in a coastal shallow-water area within was identical. Another complicating factor is that the one single geological period – the Silurian. Beneath the Silurian beds, drilling has revealed older sedi- deposition of large amounts of sediment caused the ments of Ordovician limestone, Cambrian shale and displacement of the shoreline, thus shifting the focus sandstone, as well as Precambrian layers resting on of deposition towards the south east. the crystalline basement 700 – 1000 metres beneath the ground surface.

Geotourism highlights of Gotland 11 Reef Formation During the Silurian Its rate of growth was fast at first, but decreased as it approached the surface of the water, where surf shat- An organic reef is an ecosystem in the sea, consist- tered the skeletons. The estimated average growth rate ing of a fixed core of skeletal material from dead of a modern reef is one metre per 1000 years. Many reef-building organisms, to which living generations nektonic, and benthic crawling and sessile animals of these animals and algae are attached. Free living like cephalopods, snails, brachiopods and bryozoans animals are found in the crevices on the surface and thrived in a reef environment where they could seek around the reef. food and shelter among the reef builders and in the Present day tropical coral reefs are the marine equiv- cavities. alent of the tropical rain forest, and are one of the Sea lilies () were sessile animals, often found ecosystems on earth richest in species. 430 million in large numbers on reef slopes. When they died their years ago the biodiversity in the reef was also enor- calcareous skeletons were piled up against the sides mous, although the main reef-builders differed from of the reef. Today these skeletal deposits can be seen recent ones. Today, constitute the core of the as coarse-grained fragmental limestone next to the reef, whereas in the Silurian the reefs were mainly reef limestone, consisting almost entirely of reddish dominated by stromatoporoids, a sponge-like animal, sea lily fragments. This limestone is estimated though in some cases by calcareous algae and tabu- to have been deposited at the rate of 0.5 m per 1000 late corals. The large reefs such as in the Östergarns- years. landet area, were mainly formed by stromatoporoids, Further out from the reef, shattered smaller skeletal whilst the two small – and also oldest – reefs in the parts of reef dwellers were deposited. These can marlstone on the northwest coast of the island were now be found in the stratified limestones that suc- mainly dominated by tabulate corals. ceed the fragment limestone further out from the reef Present day reef formation requires a water temper- limestone. On the sheltered landward side of the reef ature of about 22 – 28 degrees and not too great a there was a shallow lagoon where a rich animal life depth, normally not more than 20 metres, so that sun- thrived, and where calm waters enabled the sedimen- light can penetrate to the sea floor. Most modern cor- tation of the finest particles. The marlstone formed in als live symbiotically with green algae, thus requiring this way may have been deposited at a rate of 10 cm light in order to grow. It is widely believed that these per 1000 years. prerequisites could also be applied to Silurian reef When the environment altered, owing to silting up formation. or water turbidity caused by increased sediment dis- Certain periods have provided favourable conditions charge from land, the reef community was destroyed. for reef formation. At a suitable depth, sessile organ- When conditions once again became favourable isms with calcareous skeletons began to grow on for reef-building, the new reefs were formed further the sea bed. Gradually as these died, new animals towards the south east, since silting up caused the established themselves on the hard surface of the cal- displacement of the coast line – and thereby the careous skeletons. As new generations of skeletons optimal depth for reef formation – in that direction. accumulated, the reef grew in an upwards direction. Five such periods of reef formation occurred in the

12 Fostering Geotourism on the Central Baltic Islands Gotland area during the Silurian. These reef genera- tions can now been seen as parallel northeast-south- Fårö westerly stretches of reef limestone. The reef generations on Gotland differ from each other in several ways. They have been divided into three main types, named after the locations from which they have been described: the Visby reef type A is less than 10m2 in area and is dominated by corals VISBY and algae. The Hoburg reef type is up to 100 m2 and contains a large number of species; stromatoporoids, corals and calcareous algae are dominant reef build- ers here. The Holmhällar reef type is dominated by stromatoporoids and calcareous algae, but otherwise has few species. It is up to 1000 m2 and is considered Lilla to be equivalent to today’s barrier reefs, such as the Karlsö

Great Barrier Reef off Australia. Stora Karlsö

limestone facies THE Sedimentary rocks of Gotland marlstone facies

A meticulous survey of the bedrock of Gotland was sand- and siltstone facies conducted by the geologist Johan Ernhold Hede at the bioherm/biostrome facies beginning of the 20th century. The island had, how- ÖJA 0 10 20 km ever, been visited by a British geologist at an earlier HAMMARSHAGEHÄLLAR date. Sir Roderick Impey Murchison, mainly known B for having given the Silurian system its name, spent a couple of days on the island in 1845. He realised that Simplified map of the bedrock of Gotland and schematic the strata dipped gently to the south east, and con- cross-section showing the dip of the different sedimentary rocks. Note that the lower parts generally consist of easily cluded that the oldest rocks were in the north west of eroded marlstone and elevated areas of resistant limestone Gotland, whilst the youngest were in the south east. (adapted from Eliason 1999).

VISBY STENKUMLA HEJDE HAVDHEM ÖJA HAMMARS- HAGEHÄLLAR

A sea level B limestone marl reefs

Geotourism highlights of Gotland 13 14 Fostering Geotourism on the Central Baltic Islands Geotourism highlights of Gotland 15 Loose slab at cliff foot in Tunguhuvud, Fårö showing a typical fossil assemblage associated with a reef. Mapping was delayed, however, owing to difficulties highly fossiliferous, and when the cliff wall crumbles, in interpreting the bedrock. the well-preserved corals, brachiopods, gastropods, Hede divided the sediments of the island into 13 etc. are washed down onto the beach, where they stratigraphic units, and each unit was named after a can be collected with ease. local place or parish. Obviously, considerable geo- When the marls of the Visby formations were formed, logical research has been undertaken on Gotland intense volcanic activity was in progress both in the since then, but Hede’s classification is still largely island arc situated south of the and in the used to this day. north west, where the collision with the North Ameri- can plate was just taking place. Ash from the volcanic Lower and Upper Visby Formations eruption was spread over large areas. When the ash settled on the sea floor, the fauna there was probably During the Llandovery, the first quarter of the Silurian wiped out. It has now been consolidated into light period, calcareous clay was deposited in the Gotland grey bentonite clay, and can be seen at several hori- area. This can now been found as a reddish marlstone zons in the marl. Bentonite is most easily discernible in the sea along the north west coast of the island. following rainfall. Under a knife-sharp horizontal The oldest formations exposed on Gotland today boundary, the cliff is dark-coloured, due to dampness. were formed at the end of the Llandovery, and are Above, it is quite dry. Rainwater flows down in the called the Upper and Lower Visby Formations. These cracks in the rock, but when it meets a bentonite bed, fossiliferous marlstones become increasingly calcare- penetration is not possible, since damp bentonite ous towards the top of the sequences. In the Upper swells and becomes dense. The water must find an Visby Formation, the earliest reef-like formations can alternative escape route out to sea along the top of also be found. These reefs – evidence of shallowing the bentonitic band, then down the cliff walls. water – have been interpreted as the result of isostatic The small, less than 10 m2, reef knolls that occur in uplift. The alternation of argillaceous (calcium-poor) the younger parts of the Upper Visby Formation are and calcareous limestone is a frequent occurrence in dominated by tabulate corals and algae. the Gotlandic stratigraphy. A recent alternative inter- pretation of these cyclic changes is that global fluc- tuations in climate, which influence the temperature Högklint Formation and chemical content of the sea, as well as the rate of Resting on the marls is the protective cap of the erosion of the land, are responsible for the interstrati- harder Högklint Formation. These strata, roughly 35 fication and the difference in faunal content of the m thick, are largely formed of more or less connected argillaceous and calcareous strata. reefs, up to 100 m2 in size, with surrounding layers The Visby formations are together 24 metres thick, of limestone. Stromatoporoids, corals and calcareous and they can be seen in the lower part of the cliffs in algae were the dominant reef-builders, whilst crinoi- the north west of Gotland. They are thin, horizontal dal limestone can be found along the sides of the bands of soft, blue-grey marlstone, with embedded reefs. The Högklint Reef stretched along the coastline nodules or lenses of grey limestone. The sediment is in a SW – NE direction. This might indicate that the

16 Fostering Geotourism on the Central Baltic Islands contemporaneous coast north of the area ran in the Succession and ages of same direction, since the optimal depth for reef for- major rock units on Gotland mation occurs at a specific distance from the land. Global subdivisions of GOTLAND STRATIGRAPHY The Great Barrier Reef in Australia is a present day the Silurian System Rock Succession example of a reef that runs parallel with the coast- submarine rocks line. The youngest Högklint strata were deposited as south of Gotland inner offshore, shallow water sediments. The Pterygo- 420 Ma Sundre Formation (million years ago) tus beds, in which fossils of sea scorpions and even Hamra Formation Stage scorpions have been found, are examples of these. Burgsvik Formation Ludfordian Eke Formation

Tofta Formation När Formation The next unit is the Tofta Formation. It is only 8 metres thick and has a limited distribution in northern Gotland. They also indicate a very shallow deposi- Group tion environment, since they largely consist of algal limestone, a limestone comprising large calcareous Corstian Stage nodules, a couple of centimetres in diameter, made LUDLOW SERIES up of a series of coatings around shelly fragments. The 425 Ma Tofta Formation might well be partly contemporane- Klinteberg ous with the Högklint Formation. Formation

Halla Slite Group Fröjel Forma- Formation tion The Slite Group reaches a maximum thickness of Bara Oolite 100 metres, and is thus widespread in northern and Homerian Stage central Gotland. It consists of a complex of several SILURIAN SYSTEM different types of limestone, formed in varying condi- Slite Group tions; hence it is referred to as a group rather than formation. The stone industry in the north of Gotland quarries most of its stone from layers of thick-bedded, largely unfossiliferous limestone. These strata and the Formation WENLOCK SERIES pure limestone of the Högklint Formation together Tofta Formation form the areas of flat, rocky ground and the barren Högklint Formation pine forest areas in northern Gotland and Fårö. The Upper Visby Sheinwoodian Stage cement industry prefers marl-rich limestones. The Formation 430 Ma LLANDOVERY SERIES Lower Visby marl-rich, often highly fossiliferous units of the Slite Stage Formation Group can be found in the southern and eastern parts subsurface

Geotourism highlights of Gotland 17 of the area, and form the basis of the arable soil of the the Halla Formation; they disappear completely about plains of Roma. The Slite Group is considered to have 5 km north east of the church. The Mulde Brickclay been largely deposited on a steadily-rising carbonate Member was probably formed in a similar deposition platform by periodic storms. In the Slite vicinity and environment to that of the Visby formations. Earlier along the coast to the north runs a stretch of hard reef interpretations based on the depth of water will most limestones that has produced an undulating terrain, likely be revised in favour of explanations based on and the only archipelago Gotland has to offer. variation in supply of sedimentation in connection with large-scale changes in the climate.

Halla Formation

Overlying the southeastern parts of the Slite Group Klinteberg Formation is a 15 metre thick sequence deposited in shallow In the southwestern part of its range zone, the Klin- water. The lowermost part is called the ‘Bara oolite’ teberg Formation is developed as reef limestone con- and is a white so-called oolitic limestone with very sisting mainly of stromatoporoids and tabulate corals. small reef knolls enclosed. Above are brownish argil- Thick layers of coarsely fragmented crinoidal lime- laceous limestones with reefs, and at the top there are stone intercalate the reefs. Towards the north east the grey argillaceous limestones and marl. Towards the reef-predominant limestone transfers to a sequence southwest the Halla Formation thins out, disappearing consisting of different stratified limestones, rich in completely in the area to return to view in the calcareous algae, and with a large number of the bra- form of reef limestone and stratified limestone on the chiopod Conchidium biloculare. The Klinteberg For- Karlsö islands. mation is 70 metres thick, and the highest elevations At the top of the Halla Formation lies the 25 metre of central Gotland can be found in this unit. thick Mulde Brickclay Member, called the Mulde Beds or Mulde Marl in the older literature, since this Hemse Group homogeneous strata unit consists of bluish-grey lay- The 100-metre thick Hemse Group, like the Slite ers of soft marlstones, alternating with thick layers of Group, consist of limestones towards the north, grey to blue-grey, argillaceous, compact limestones. and soft marlstone towards the south. The limestone The marl is rich in well-preserved fossils, mainly bra- sequence comprises different types of stratified lime- chiopods and tabulate corals. Small trilobites, rolled stone and reef limestone. The Östergarn area is com- into a ball, are not unusual, although the location that posed of enormous reefs, mainly consisting of stro- was by far the best for trilobites on Gotland, where matoporoids. the Mulde brickyard once lay, has now been filled in. The Mulde Brickclay Member is best viewed in Crinoids are abundant in the limestone area, just the cuttings along the coasts of Fröjel and . The as bivalves, including Ilionia prisca and the large strata thin out and become more limestone-domi- nated towards the north east. At Klinte parish church Stratigraphic map of Gotland (adapted from they are less than 1 m thick and overlie the rest of Eriksson & Calner 2005 and Erlström et al 2009).

18 Fostering Geotourism on the Central Baltic Islands Generalised geological Fårö map of Gotland

SLITE

VISBY

Slite Group

KATTHAMMARSVIK

KLINTEHAMN Stratigraphy Klinteberg Formation

Lilla Karlsö Sundre Formation

Hamra Formation

Stora Karlsö Burgsvik Formation

Hemse Group Eke Formation

Ludlow Hemse Group

Klinteberg Formation

Halla Formation

Fröjel Formation

Slite Group BURGSVIK Hangvar Formation

Tofta Formation Wenlock Högklint Formation

0 10 20 km Lower & Upper Visby Formation Megalomus gotlandicus, can be found in abundance the so-called Rhizophyllum-limestone, can be found in some other areas, as in the shell deposit at Kat- on the isolated elevations of the Eke Formation in the thammarsvik harbour. In the south, the limestone is north east, as at Lau backar. replaced by reefs and a fairly homogeneous marl- stone sequence of thin layers, nodules and lenses of Burgsvik Formation limestone. Graptolites, otherwise rare on Gotland, The Burgsvik Formation, reaching a maximum thick- can be found in the marl. ness of 50 metres, is exposed along a narrow strip, mainly in the southernmost part of the west coast of Eke Formation Gotland. It stretches up to Grötlingbo, with a couple The Eke Formation is characterized by an abundance of isolated areas, known as outliers, at Närsholmen of calcareous algae, indicating a shallow depositional and at Burgen in Burs. The Burgsvik Formation mainly environment. The strata, no more that 15 metres consists of fine-grained calcareous sandstone, often thick, consist of bluish-grey argillaceous limestones intercalated with thin beds of bluish clay. In many and micaceous marls. Crinoidal limestone, marlstone places, the sandstone is overlain by oolitic lime- and argillaceous limestones with small reef knolls, View to the north from top of Hoburg cliff.

20 Fostering Geotourism on the Central Baltic Islands stone or alternating layers of sandstone and oolites. as opposed to the sandstone, is highly fossiliferous, In the northeasterly outliers, which are no more than including brachiopods, bryozoans, bivalves and frag- 8 metres thick at most, the strata mainly consist of ments of the large trilobite Homalonotus. oolitic, arenaceous, partly conglomeratic limestones, When the Burgsvik Formation was deposited, the (containing large pieces of rounded fossils), as well continental collision between the North American as reef and crinoidal limestones. The sandstone is and North European plates was reaching its end and poorly fossiliferous but shell deposits, mainly of the the Caledonides, the mountain range resulting from bivalve Pteronitella retroflexa, can be found here and there. Sedimentary structures, such as cross the collision, were being pushed up in the north. Ero- bedding, (inclined at steep angles to the dip of the sive powers were already at work, and eroded prod- strata), and ripple marks are usual, as well as trace ucts from the mountain range were washed out into fossils of burrowing animals. In the sandstone, some the sea, some of them to form these sandy deposits extremely interesting finds have been made of fin- in the area of Gotland. The sediments were depos- spines, armour plates, teeth and scales from the rare ited in shallow water close to land, partly as beach spiny dogfish (acanthodians) and ostracoderms that sediment. Subsidence structures bear witness to how lived here during the Silurian. The oolitic limestone, movements in the earth’s crust caused the collapse of

Geotourism highlights of Gotland 21 the sediment before it had lithified. In the Burgsvik mation. However, most of these younger beds were sandstone and oolite, spores of terrestrial plants have worn away by erosion at a later date. been found, representing some of the oldest evidence Beneath the Silurian deposits there are older beds of of the plant conquest of land. limestone and sandstone, formed during the Ordovi- cian and Cambrian. This entire block of sediment dips Hamra Formation to the south-east, causing the edge of the Ordovician beds to rise up and form the island of Öland, while the The basal part of the 40 metre thick Hamra Forma- Cambrian beds are exposed along the coast of tion contains algal limestone, succeeded by argilla- and at certain places along the west coast of Öland. ceous limestones and capped by reef and crinoidal limestone. Thinner layers of Hamra limestone can be found in the outliers at Burgen and Närsholmen, Gotland Fossils where they have developed into reef limestone. More than 2000 fossil species have been described from Gotland, but because the only preserved organ- Sundre FormationThe Sundre Formation forms the isms are mostly those that had mineralised shells or youngest parts of the bedrock of Gotland. The strata, skeletons, this figure does not reflect the probable no more than 10 metres thick, consist of stromat- original diversity of life during the Silurian Period. oporoid and algae-predominant reef, surrounded by We have very little knowledge of the probably large crinoidal limestone. The beautiful, red, glittering sea numbers of soft bodied animals, and plants such as lily limestone has been quarried under the name of algae, that lived here in the shallow marine environ- Hoburg marble and used for sculptures and deco- ments of that time; soft tissues generally decay rap- rative purposes in buildings such as the churches idly and are very rarely preserved in the fossil record. on Gotland. Only small quantities of the stone thus Trace fossils from the activities of soft bodied organ- remain, although beautiful specimens can still be isms, such as burrows and digging tracks in the sedi- found amongst the rubble that has been discarded ment, are mostly the only proof of their existence. in the marble quarry at Hoburgen, for example. The Algae were certainly very common, but only those sea stacks along the south and southeast coasts, as at that produced lime in their tissues – the calcareous Hoburgen and Holmhällar, are of sculpted Sundre reef algae – were preserved commonly, for example as limestone, which was deposited during early Ludlow. substantial components within reef bodies where Sedimentation must, however, have continued in the they performed an important function in binding sed- area, since contemporaneous cracks in the sediment iments together. However, microscopic spores from have been filled with calcareous sediment that has algae and even from primitive land plants have been proved to be younger than the rest of the Sundre For- found on Gotland.

Typical fossils found in the bedrock of Gotland: A – Stromatoporoid, B – Halysites coral, C – Rugose coral, D – Ortho­ ceras cephalopod, E – Rugose coral, F – Gastropod, G – Heliolites coral, H – Bivalve Pteronitella retroflexa, I – Gastropod Loxonema, J – Gastropod, K – Brachiopod Leptaena, L – Rugose coral, M – Trilobite Calymene, N – Brachiopod Janius, O – Brachiopod Visbyella, P – Ostracod Hermannina, Q – Broken crinoid stems, R – Broken crinoid stem, S – Coenites coral, T – Palaeocyclus rugose coral. Photo: R. Hejdström.

22 Fostering Geotourism on the Central Baltic Islands A

B

C

E D

F G H

I J

K

M N L O

T S

Geotourism highlights of Gotland 23 P Q R So, what kinds of fossils are most common? Of course disintegrated, to be incorporated as common compo- this varies between different places and in different nents of limestone sediments. kinds of rock that reflect different original environ- Corals are naturally associated today with tropical ments. Reef limestones are built mostly from robust, reefs, but in the Silurian different types of corals were skeletal animals such as colonial corals and stro- equally common in the off-reef, soft bottom environ- matoporoids, while the marlstones represent a rela- ments. There were two main groups of Palaeozoic tively soft bottom, low energy marine environment in corals. Rugose corals were mostly solitary forms, gen- which brachiopods, trilobites and other bottom-liv- erally with conical skeletons (theca) whose distinctive ing organisms were generally more abundant. Some shape has given them the popular name ‘tomteluvor’ fossils can be so common in certain sediments that (Santa caps). One particular species however is quite their fragmental remains alone build up whole beds different and distinctive, occurring only in the oldest of limestone. For example, the sea lilies (crinoids) beds along the northwest coast; this is Palaeocyclus, a lived crowded in some beds and on reef slopes in small button shaped coral that has the popular name such huge numbers that their skeletal remains now of ‘knappkorall’, and it is an important indicator of form coarse fragmental limestones that are sometimes late Lower Silurian age in rock successions across referred to as marble, such as Hoburgsmarmor and much of the present North Atlantic region. Karlsömarmor – used especially as decorative and building stone. Tabulate corals were colonial forms, living in reef environments and on the soft seabed and whose The most common fossils in the reef limestones are skeletons vary in size from a few centimetres to tens stromatoporoids. These compact, conical, sub-spher- of metres. Best known examples are the chain coral ical or sub-laminar skeletons were built up in con- Halysites together with Favosites and Heliolites, all centric calcareous layers by a sponge-like tissue; they with distinctive shapes of the skeletal openings. are also widespread in bedded limestones. Stromat- oporoids have a particular place in Gotland folk his- Brachiopods (often referred to as Lampshells) are tory. In the burning of lime the inner hard parts of the bivalved shells, of which about 200 species are fossils were commonly left unaffected by the burn- known today, but over 30 000 fossil species are ing, and the spherical remains resembled the skulls known from Palaeozoic rocks and they are very com- of cats, from which the stromatoporoids derived their mon on Gotland. The two valves are of unequal size, popular name as ‘kattskallar’. with the larger, or pedicle valve having a distinctive aperture in the beak through which a soft fleshy stalk The sea-lilies, or crinoids, were very common in emerged (the pedicle) to anchor the animal to the sea Silurian tropical seas. These echinoderms were also bed. associated primarily with reefs, anchored to the reef slopes or sea floor by a long, segmented flexible stalk, The Bryozoa (‘moss animals’) are small colonial which supported a cup shaped body (theca). Five flex- organisms that commonly live attached to other ani- ible feather-like ‘arms’ diverged from the theca as the mals, plants or other objects. Some of the colonial food gathering apparatus. After death the soft tissue skeletons have a superficial resemblance to tabulate decayed and the many components of the skeleton corals, but the individual chambers are much smaller.

24 Fostering Geotourism on the Central Baltic Islands The Bryozoa are possibly related to the brachiopods. remarkable to realise that when the rocks and envi- They are very common in limestone and marlstone ronments of Gotland were being formed over 400 sediments on Gotland, although generally frag- million years ago, all known major groups of organ- mented. isms (phyla) that exist today were already in exist- ence. Gotland provides abundant fossil evidence in Molluscs are well represented among the Gotland support of this understanding of the development of fossil faunas. The most common group is the Gastro- life on earth. poda (as marine ‘snails’), found preferentially in marl- stones. They are fairly easily recognised by their spiral shells, some as slender vertical spirals and others as Later Geological Periods more robust, horizontally coiled and generally larger and the Ice Age forms as in the genus Euomphalopterus. Bivalvia Once Scandinavia and north-western parts of the Bal- (‘lamellibranchs’) are less common, but can be tic basin had risen above sea level to form a large found occasionally in mussel beds at some horizons. area of land at the end of the Caledonian orogeny, Cephalopoda – essentially as fossil ‘squids’ belonging a long time passed during which Gotland has no to the genus Orthoceratites – are not uncommon in sediments and thus no historical geological record of the Gotland rocks, although mostly as a few cham- the area and its life. It was not until the very recent bers of the originally longer, straight tubular shells; Quarternary period from 2.6 million years up to the many specimens retain detail of the concave chamber present day, that more sediments were deposited on walls (septa) that were secreted as the animal grew. Gotland; dominated by the inland ice ages as is typi- Trilobites are an extinct group of arthropods, common cal for northern latitudes in this period. These gla- in the Palaeozoic seas but which became extinct at ciations took place on probably six occasions, each the end of the Permian Period. They are seldom found lasting about 100 000 years. During the ice ages, as complete specimens, but they are fairly common shorter periods of warmer climate did occur – known throughout the Gotland sequence. Moulted segments as interstadial periods, when even vegetation colo- of the body are not uncommon at many levels, and nised the areas from which the ice had temporarily heads and tails are easy to recognise. The furrows that retreated. Each time the glaciers crushed, ground, and divide the body into three longitudinal segments are transported the bedrock, traces of previous glaciation equally well defined in most specimens. were largely wiped out, meaning that we are most Apart from the main groups of fossils outlined above, knowledgeable about the latest glaciation. there are various other groups known but which are The latest glaciation took place during the Weich- rare or require specialist techniques to extract them as sel Ice Age, that lasted until 10 000 years ago. At its microfossils. For example, primitive fishes are known greatest extent, glaciation stretched right down to from fish scales, conodonts are part of the tooth appa- with an ice-mass several kilometres thick. The ratus of fishes, there are sea scorpions (Eurypterida), enormous weight depressed the earth’s crust by about mussel shrimps (Ostracoda), early plant spores, and 800 metres, and when the glacier began to thaw, it primitive molluscs known as Monoplacophora. It is started to rise back to its normal position. This iso-

Geotourism highlights of Gotland 25 static rise is still in progress in large parts of Scandi- fisher-gatherers became increasingly widespread in navia, albeit at a significantly slower rate. Scandinavia, as well as on Gotland. As the gradual

Since an enormous bulk of water was locked up elevation of the land diminished the size of Öresund in the inland ice, the sea water level was over 100 and Stora Bält, salinity slowly decreased until we metres lower than today, and Öresund and Stora Bält eventually reached the brackish water stage that pre- were still dry land, when the ice retreated from the vails in the Baltic Sea today. south of the Baltic Sea area. Glacier water from the retreating ice mass filled the Baltic basin, and was Quarternary Deposits dammed by the ice-front in the north and the newly- The inland ice deposited the loose soil cover of the formed dry land areas in the south. Since there was Scandinavian and Baltic countries. The cold climate no outlet to the oceans, the surface of the Baltic at the beginning of the Ice Age meant that the snow Glacial Lake rose at a higher rate than the sea level, in the north did not thaw away, but accumulated in until the thawed ice-front passed the northern tip of glaciers that increased in size and spread out fur- the Swedish mount Billingen 11 500 years ago. The ther and further away from the mountain areas. The glacial lake was then drained into the newly formed ice sheet was in constant motion and its enormous connection with the sea, whereupon the water level weight provided forces that ground and smashed the sank by 25 metres. bedrock in its southward path. With increased pres- The ice first started melting in fluctuating climatic sure, the ice at the very bottom melted, helping the conditions. Temporary ice sheet thrusts sometimes ice mass to slide more easily on its base. The uneven- interrupted the melting process, making the process ness of the bedrock with elevations and depressions more complicated than described here. caused constant changes in pressure. When pressure The saline sea stage that succeeded the Baltic Gla- was eased on the leeward side of a hillock, the basal cial Lake is called the Yoldia Sea, after the glacial sea ice froze again, and the material shattered by the ice bivalve Yoldia arctica (now known as Portlandia arc- and mixed with the icy slush then became embed- tica) that can be found in the sediment from this time. ded in the ice and followed the movement of the ice Land elevation in the ice-free areas was now swift, mass. In this way the ice could transport large boul- soon equalling the rise in sea level. The Baltic Sea ders, stones and gravel for hundreds of kilometres. basin was again cut off from the ocean owing to land The embedded material could act as abrasive par- elevation in central Scandinavia about 10 700 years ticles, scouring the rocks beneath as the ice surged ago. This stage has been called the Ancylus Lake, after forward, producing the that indicate the the freshwater gastropod Ancylus fluviatilis. Contact direction of movement of the ice. When the climate with the sea was again established 10 000 years ago gradually became warmer, the ice melted at the edges via the Danish Sound, forming a sea called Littorina at a quicker rate than it expanded in the north, lead- Sea after the littoral shell Littorina littorea that can be ing to the deposition of the embedded material. This found in its sediments. The post-glacial warm period unsorted sediment of boulders, stones, gravel, sand occurred at this time, and people living as hunter- and clay is called till.

26 Fostering Geotourism on the Central Baltic Islands On the sunlit surfaces of the shrinking ice mass, a Fårö flow of melt water was formed. This plunged down Ancient shorelines cracks in the ice where it collected to form glacial on Gotland streams that flowed out to the snout of the glacier. The sediment in the ice followed the strong currents of the streams, to be deposited at the bottom of the cracks as the current velocity decreased, thus sorting SLITE the material according to grain size. When the glacial VISBY stream finally reached the snout of the glacier and the flow abated, sand was deposited in a delta out- side the snout of the glacier. Clay particles, the finest material, were kept in suspension until all movement KATTHAMMARSVIK ceased, when they were deposited as a clay sediment on the bed of a glacial lake. The results can be seen KLINTEHAMN today as glacial stream deposits, such as eskers and Lilla Karlsö outwash plains, as well as varved (finely layered) clay Stora Karlsö deposited by the glacial lake.

Landscapes of Gotland today Ancylus Lake highest shoreline Littorina Sea highest shoreline BURGSVIK The landscape of Gotland has been formed through present-day area different processes during several phases. The large 0 10 20 km scale forms of today’s landscape were created already during the time when the bedrock was a soft bottom sediment in a tropical near shore sea 420 – 430 mil- Showing distribution of beach ridges that can be used to lion years ago. The marlstone rocks tend to be eas- reconstruct former coastlines through time (adapted from ily eroded and form flat-lying areas, while the pure Eliason 1999). bedded limestones and reefal units are much more lions of years. Movements in the crust also affected resistant. Owing to the alternation of these rock types the Baltic region in other ways. Earthquakes created described above, the topography of Gotland is thus faults and cracks formed in the bedrock. In the bed- broadly divided into five regions: the hard limestones rock west of Gotland there are traces of several faults. form elevated areas in the north, middle and far south These have formed gorges in which rivers flowed at of the island, separated by two large low-lying areas certain times, which then continued to erode the bed- that lie either side of the central elevated region. rock. Gotland’s north-west cliffs are a result of these Over millions of years following the sedimentation events. The entire island is also traversed by cracks on the seabed the sediments were lithified, and sub- and many deep bays are formed by erosion of weaker jected to the erosive force of water and wind over mil- fracture zones in the bedrock.

Geotourism highlights of Gotland 27 28 Fostering Geotourism on the Central Baltic Islands

Coastal cliffs at Sigsarvestrand, NW Gotland. Geotourism highlights of Gotland 29 The Baltic Sea and the sea coast species coexist, but under physiological stress, while they are not really adapted to the low salinity. There- Gotland is, like all other islands, heavily influenced fore, the marine species in the Baltic Sea are generally by the surrounding sea water. The climate is control- smaller in body size than they would have become if led in part by water temperature. Spring is delayed by they lived in saline water. On the other hand, marine the cold water mass, which on the other hand, once animals living in this environment are often very suc- it has been heated, prolongs the mild autumn. The cessful in terms of number of individuals, since they surrounding sea is also a barrier to migrating species. have little competition from many other species. This has given Gotland a rather poor but interesting fauna developed in isolation from other populations. The Coast The Baltic Sea is a young sea. When the ice began to retreat about 15 000 years ago, the Baltic basin was Gotland is for many tourists equated with beautiful, filled with water from the melting ice. The Baltic Ice often dramatic coastal sceneries. The 550 km long Lake was established. This first stage in the develop- coastline (770 km long if you include Fårö, Stora ment of the Baltic Sea was replaced by alternating and Lilla Karlsö and other fairly large islands around salt water and freshwater stages until today’s brack- Gotland) varies depending on the bedrock, soils and ish water stage. Characteristic of this young sea with landforms. It consists of alternating barren shingle low salinity is low diversity, with very few brackish beaches, steep cliffs, soft inviting sandy beaches and water species. Instead, freshwater species and marine flat bird-rich beach meadows.

30 Fostering Geotourism on the Central Baltic Islands The broad outline of the coast is primarily formed by stantly exposed to the erosion of the sea waves, ice large-scale fault movements and river erosion in Pal- and rain water. When enough material has been hol- aeogene and Neogene time, long before the Ice Age. lowed out from the cliff, the overlying limestone col- The shape of the coast is also determined largely by lapses and falls down on the beach, forming piles of the nature of the rock. Where bedrock is composed of rocks. Huge boulders of reef limestone are particu- hard bedded limestone and reef limestone the coast is larly common underneath overhanging cliffs. Weath- rocky, often with sharp cliffs. Where bedrock is com- ered material from the marlstone forms screes at the posed of softer marlstone the coast is flat. foot of the cliff. The beach is covered by shingle, often forming beach ridges.

Coastal Cliffs Outside the shoreline the water often covers a flat The western and north-west coast, from Gnisvärd in rock surface. This bedrock shelf, an underwater cliff, the south to Hallshuk in the north is about 50 kilo- extends, at a depth of more than half a metre, from metres long and is dominated by up to 40 metres 20 to 200 metres out from the coast. At this point high sharp cliffs. The uppermost part of the pro- the edge of the underwater cliff steepens into a drop truding cliffs consists of resistant reef limestone. In of several dozen metres. At certain wind conditions, between them, the upper part of the cliff consists of when there are strong onshore breezes, dangerous thick bedded limestone. Underneath, there is the underwater currents can form outside the cliff edge softer fine layered marlstone. The marlstone is con- that can trap people bathing.

A wedding ceremony taking place in the Folhammar area, eastern Gotland.

Geotourism highlights of Gotland 31 Colossal, ring-shaped depressions, so-called ‘Philip Sea Stacks structures’, that are visible on the top surface of the In many places along the coast, where the limestone underwater cliff all along the northwest coast, indi- cliffs meet the sea, the water has not been able to cate the former existence of reefs. These structures, wear down the cliff in its whole. The resilient reef most clearly visible from the air, are actually parts of limestone remains as stone statues – sea stacks or limestone beds, which once were pressed down by ‘raukar’. These often occur in groups to form sea- the weight of overlying large reefs, which have now fields. One can often see that all stacks within a been eroded away. group reach the same height, which shows the origi- Coastal cliffs, albeit modest in height, can also be nal cliff top level before the water erosion. The larg- found along other parts of the coastline. In Eksta for est sea stack field is found along Digerhuvud on the example, the Mulde Brickclay Member forms a low north-west coast of Fårö. Langhammarshammar, also cliff along the coast. Wherever the coastal bedrock on Fårö, is the most famous and photographed sea consists of pure limestone with reefs, as it does at stack field. Other scenic sea stacks along the coast the northeastern, eastern and southernmost Gotland can be found in Lickershamn, Lergrav, Kyllaj, Folham- coastline is rocky, sometimes with sharp cliffs. mar, Holmhällar and Hoburgen.

32 Fostering Geotourism on the Central Baltic Islands Shingle Beaches Since all soil is washed away from the gravel, very few plants can live in the arid and nutrient-poor envi- Shingle beaches are the most common type of ronment of a shingle beach. Seaweed ridges washed beaches on Gotland. These are found beneath the up on the beach, however, have a nutrient demand- coastal cliff and along other stretches of the coast of ing flora including nettle, curled dock and various Gotland, where the bedrock consists of hard lime- oraches. In the past seaweed, called släke, was used stone. Rubbles of limestone from the bedrock are as fertilizer on fields. Despite the barren environment, mixed with igneous rocks and sandstones transported to the island by the inland ice. They form beautiful many birds breed here. sea walls that may extend far up on land. The ridges far-away from the coastline were thrown up by storms Sand Beaches during earlier stages of the Baltic Sea, when the water level was higher. As the water retreated, new beach Sandy beaches are found in bays along the Gotland ridges washed up below and parallel to the elderly. coast and the whole coast of northeastern Fårö. The Such systems of beach ridges can be found in many sand, which largely consists of quartz grains, origi- parts of the island, sometimes they are completely nates from eroded rocks on the Scandinavian main- covered with forest. land, and was initially transported to the island by the

Geotourism highlights of Gotland 33

Sea shore meadow at Falluden, eastern Gotland. inland ice. The sand was deposited in the bays as the Sea Shore Meadows energy of the water transporting it decreased. Sand Sea shore meadows are found along the flat coastal deposited by the large glacial rivers during the ice areas of Gotland, particularly in the southeast and melting period forms widespread sandy areas, such southwest of the island. Here the bedrock consists as the northern Fårö, Salvorev and Gotska Sandön. of softer marlstone, eroded by former glaciers, and Sandy beach environments are harsh. The waves keep now covered with a clayey soil. The beach meadows the sand in constant motion and it is difficult for land used to be important pasture and hayfields. Haymak- plants and algae to find ‘foothold’. Further up the ing and pasture kept them open, thus favouring the beach, where waves do not reach, some herbs such as flora and fauna. Now EU-subsidies helps the farmers sea sandwort and sea rocket, grow. Both are adapted to keep these valuable coast areas open. Sea shore to the dry sandy environment by having fleshy leaves meadows are self-fertilizing by floods washing up with a relatively small area to prevent evaporation. nutritious seaweed on the flat beaches. On top of the dune the grasses lyme-grass and mar- ram are growing. Their deep root system makes them The flora of the sea shore meadows is very diverse. resistant to sand drifts. If they are buried by sand, they Many plants are adapted to withstand grazing, oth- quickly shoot up new shoots to the surface. ers are capable of tolerating high salt concentrations.

34 Fostering Geotourism on the Central Baltic Islands

Hejnum hällar in June. After repeated floods, salt concentration can be very ous forests are relatively modest. If you compare a high in the hollows, where trapped seawater evapo- map of forest distribution with a geological map you rates and leaves behind salt. will see that large coniferous forests grow on areas of harder limestone. This bedrock is covered with lime- The is a coastal biotope where a lot of rich till, which favours pine ahead of spruce that are birds thrive. In the fine-grained and nutrient-rich soil not comfortable with a high pH, but require more on the shallow bottoms many bugs live that attract acidic soils. waders and ducks.

The sea shore meadows on Gotland represent a fifth Limestone Pavements/ of the total area of sea shore meadows in Sweden. In the higher lying areas of Gotland the bedrock consists of hard, resistant limestone. The soil cover The inland is very thin or absent. Trees and shrubs have difficul- Forests ties in establishing themselves on the rocky ground, Nearly half of Gotland’s surface is covered by forests. which therefore remains more or less open. Grazing Coniferous forests, with pine as the dominant tree animals, especially sheep that live outside all year species, are most common, while areas with decidu- around and even eat woody plants, have helped to

Geotourism highlights of Gotland 35 keep the landscape open for centuries, and a spe- wherever there are accessible cracks or a superfi- cial habitat – alvar – has been developed. Alv is an cial soil cover, enabling the trees to take root. These ancient word describing land that is useless for culti- areas thus display a mosaic of clusters of trees, juni- vating. In Sundre parish on southernmost Gotland, in per bushes and treeless areas with exposed tabular File hajdar, Hejnum hällar on northern Gotland, and limestone slabs. The limestone plateaux of southern on Östergarnslandet in the easternmost region there Gotland are more open, often coated with thin layers are large continuous areas of alvars. Large parts of of stony soils. Fårö also have examples of how a long tradition of In former times, fields, meadows and pasturelands grazing shaped the landscape, with groves of pines close to the farms were fenced off. Ground further and cropped juniper bushes in meagre grassland. afield was declared commonland, and used jointly The absence of shading trees and the thin, sometimes by several farms for grazing. This outlying land often completely non-existent soil layer makes the rocky comprised meagre pastureland, forest and tabular grounds/alvars extremely dry in summer. Many of limestone rock. The long-term grazing of larger areas the plants have become adapted to survive the heat of the limestone plateaux led to the development and aridity of the summer. A number of plants are of a rich flora and fauna adapted to grazing. When annuals, and blossom in spring before the arrival of grazing diminished in intensity, the land gradually the drought. Stonecrops have thick, succulent leaves became overgrown, mainly with juniper and black- which store water in rainy periods. Other plants, like thorn, and the grazing-adapted plants died out, thus Vincetoxicum have leathery leaves, which minimise grossly reducing the number of species. Grazing is transpiration. necessary for the preservation of the variety of flora In winter, when temperatures fluctuate around zero, and fauna on the limestone plateaux. alternating freezing and thawing cause movements in Changes in land use on Gotland have dramatically the ground, which can sever roots. Some plants on altered its original character. Most decidous forests the limestone plateaux have adapted to this feature are overgrown meadows, for example. The water and have developed strong roots; these include the bodies of Gotland have also been significantly common rock rose, wild thyme and Globularia. altered. Many of the once common wetlands have Rock outcrops are traversed by cracks primarily been drained to make way for farmland; and rivers caused by structural movements in the bedrock. The and streams have had their original courses deep- cracks become expanded secondarily through chemi- ened and straightened. Of the remaining wetlands, cal dissolution by carbonic acid in the seeping rain- the largest are the Bäste and Tingstäde lakes, both in water. This is the same process that formed karst caves the north of the island. such as Lummelunda cave. The cracks are often filled with weathering soil on which many plants can estab- lish. They also preserve moisture and provide a shady habitat for plants such as the hepatica. The limestone plateaux in the north of Gotland are covered with sparse pine forests growing in clusters

36 Fostering Geotourism on the Central Baltic Islands History and Cultural Heritage Bronze Age (About 1800 – 500 BC) of Gotland Bronze, an alloy of copper and tin, was introduced Stone Age (About 7400 – 1800 BC) to Gotland from in the form of manu- Gotland was populated early in human history. Some factured articles, mostly weapons. Animal husbandry of the oldest traces of humans in Sweden are 9400 and agriculture developed, but hunting and fishing year-old skeletal remains from the Stora Förvar cave continued to play an important part in the supply of on Stora Karlsö. The first people to inhabit Gotland food. More and more land was cleared and cultivated lived on hunting, fishing and gathering. There were in the inland. many seals, fish, poultry and edible plants. Stone Age A society based on animal husbandry and agricul- Gotland was smaller than the island today, because ture, and with a more stable residence of popula- sea level was significantly higher. The climate was tion, required more organisation, as well as trade and slightly warmer than today and the landscape con- sisted of open moorland and forests of pine and craftsmanship of the precious metal. Even the large deciduous trees. There were many lakes and streams. and impressive tombs, large cairns, and ship settings, About 2000 years BC, agriculture became the main suggest that society was divided more socially than source of living and income. Around the coast of before. Together with , Gotland is the region in Gotland there are several large settlements from the Sweden where most finds of objects from the Bronze Neolithic era. Age have been made.

TheGeotourism Gannarve highlights stone ofship, Gotland 29 metres 37 long and up to 5 metres wide, dates back to Late Bronze Age. Photo: T. Bauert. Iron Age (About 500 BC – 1050 AD) surplus of produce. Barley, rye, oats, flax and hemp were cultivated. Sheep and goats, pigs, cattle, horses The Gotlanders learned to use iron from about and chickens were reared. 500 BC, and became skilled blacksmiths. Iron was cheaper and more readily available than bronze. Ara- ble and livestock farming were still the most impor- (About 1050 – 1500 AD) tant economies. During the first centuries of the Middle Ages the The climate deteriorated in the early Iron Age, which importance of Gotland in the Baltic Sea trade contin- meant that farmers had to keep animals indoors and ued to grow. At first, the rural population accounted feed them during winter. Meadows were cleared to for the majority of the trade, but during the 12th provide hay and leaf fodder. A landscape developed century the harbour of Visby became the that was dominated by fenced meadows, pastures and island’s commercial metropolis. A large influx of for- small croplands near the farm. The animals grazed in eign merchants contributed to the growth of the city the woods and on the limestone pavements. The cul- as it grew in size and importance in international tural landscape that began to emerge during the Iron trade. It focused on trade between Novgorod in Rus- Age remained until the 19th century, and many rem- sia and . The trade was organized in nants are still preserved. Large longhouses with heavy the so-called , which extended over stone foundations were built on the farms. In many the Baltic region, Norway, England, Netherlands and places today one can still see the remains of house Belgium. Trading brought great prosperity both to foundations from the early Iron Age. They are found Gotland’s ‘travelling peasants’ and to the merchants usually in the meadows. Together with the founda- in Visby. tions there are often remnants of fences and burial The products that made Gotland so successful in the grounds, which had eventually been built adjacent trade were not all produced on the island but were to the farms. brought largely from the eastern side of the Baltic During the latter part of the Iron Age, in the Viking era Sea. In Novgorod, islanders from Gotland had already (750-1050 AD), trading was an increasingly impor- built a trading site in the 12th century – Gutagård, tant source of revenue for the island. Trade and crafts where Russian hunters supplied furs, and from the were concentrated in the island’s many harbours. Baltic area was bought beeswax, a coveted article for Gotland’s strategic position in the Baltic Sea made church people in the whole Christian world, where it easy for the islanders to transport the goods, and it was used for producing wax candles. In the Mid- many of the most important trade routes at this time dle Ages, skilled stone-cutters on Gotland produced through the Baltic Sea passed Gotland. Inscriptions quantities of highly artistic baptismal fonts. Over a on picture stones and other objects tell of some of the thousand fonts were exported to churches through islanders who made long journeys to distant coun- the entire Baltic Sea region. The revenue from trade tries. The travels resulted in huge profits, as evidenced led to the construction of magnificent stone buildings by the many silver treasures found on the island. The increasingly extensive agriculture resulted in a slight Excerpt from the map Livonia vulgo Lyefland, 1648.

38 Fostering Geotourism on the Central Baltic Islands Geotourism highlights of Gotland 39 both in Visby and in rural areas, and especially in the boom were demolished to provide building stone for building of over one hundred beautiful churches on the magnificent houses on rural farms and in Visby. the island. Agriculture expanded considerably during the 19th From its original organisation of merchants, the century. The growing population demanded more Hanseatic League became an international associa- grain, and the opportunity to cultivate more arable tion of cities in the late 13th century. Farmers out- land increased when chemical fertilizers were intro- side the city were no longer welcome to participate duced. Meadow land was cut and cropped, wetlands in international trade. The most important symbol for were drained and converted to farmland. The land- the break between urban and rural areas was the wall scape, dominated by meadows, pastures and small that the people of Visby built around their town. The fields, which had prevailed since the Iron Age, was controversy led to a civil war in Gotland in 1288. now changed radically. Visby residents won the battle, but already in the 14th Industrialisation reached Gotland in about 1900. century the city began to lose its importance. The Communications developed and the island was Gotlanders met increasing competition in the trade linked closer to the . Meanwhile, the effects with Eastern goods, and the plague struck the Baltic of previous visits of artists, poets and writers began to Sea region in 1350. In 1361 the Danish king, Valde- bear fruit. These groups had made pilgrimages to the mar Atterdag, conquered Gotland after clashing with ‘fairy tale island’ during the Romantic era in the late the peasants in several battles. 18th and early 19th centuries. In books and paintings they had removed the image of an isolated landscape. 1500 – 1900 AD Now the clear air, the clean health-giving water, the romantic ruins and the exciting history made Gotland Gotland was affected by further deterioration in the one of Sweden’s main centres for healthy and cultural early 15th century, not least because of large tax . increases. Over many years, the island was ruled by different Danish castle lords, often with the imposi- tion of very harsh conditions. INDUSTRIAL HISTORY OF GOTLAND When the Brömsebro peace accord was signed in There is a long history of quarrying for limestone and 1645, Gotland was returned to Sweden, a country sandstone on Gotland. Stone has been used for vari- whose territory had expanded greatly since the Mid- ous purposes since Prehistoric times. Initially, rocks dle Ages. The Swedish government now wanted to and boulders were used from blocks that lay scattered develop Gotland in military, administrative and com- on the landscape. The large Bronze Age cairns were mercial activities. built from such stone, and within them constructions It was not until the second half of the18th century of stacked limestone and cists of limestone blocks are that trading was boosted, and prosperity then really quite common. Many of the ancient hill forts are con- returned to the island. During this time, timber, tar, structed of limestone dry walling. stone and lime were sold to ports around the Baltic Smaller Iron Age cairns and dwellings – the so-called Sea coast and ruins from the 13th century building kämpgravar (‘giants graves’) – also included consider-

40 Fostering Geotourism on the Central Baltic Islands able quantities of stone, together with the stone walls close to a port, and in the 17th and 18th centuries built for boundary fencing. Limestone is considerably small cargo boats carrying burnt lime transported softer and therefore easier to carve than igneous rocks the products to Swedish, Danish and German ports. such as granite. It is no coincidence therefore that Northern and easternmost Gotland were the main the unique picture stones were produced on Gotland. areas for lime burning. Intense production of burnt Limestone was also more easily accessible, often lime led eventually to widespread deforestation, quarried in the immediate vicinity. especially in northern Gotland; the wood used as fuel was replaced later by coal. In the Middle Ages, both limestone and sandstone were important construction materials for the approx- Industrialisation in Sweden in the late 19th century imately one hundred churches that were built on brought with it an increased demand for limestone. Gotland. The Visby town walls, warehouses in Visby, The cellulose industry in particular required lime for and residential and farm buildings in rural areas were production, but it was necessary also for iron works also built of easily quarried limestones, which were and sugar refineries. Increased need for limestone then produced as blocks for construction. How- led to the opening of many new quarries in north- ever, limestone was not exported as building blocks, ern Gotland. Stone blocks from several quarries on because outside Gotland cheaper brick was preferred. Gotland were shipped to Germany, and used for But for facades and decoration, Gotland limestone example in construction of the Autobahn road net- and sandstone became major products for export. work.

Sandstone was exported in the form of grinding Cement was the next product to be developed, using stones and brows from as early as the Viking Era. Bap- limestone, clay and marlstone as raw material. The Visby cement plant was built in 1884, and in the 20th tisimal fonts made of sandstone and limestone were century the Valleviken and Slite factories were estab- exported widely through Europe in the Middle Ages. lished. The cement factory/quarrying complex in Slite In the 1500s, when held a monopoly on quar- is now the largest in Scandinavia. rying, sandstone was exported to Denmark, includ- ing construction for castles. After Gotland became a In the early 20th century, 1.6 million tonnes of lime- Swedish territory in 1645, exports of stone for facades stone per year were quarried on Gotland, and in the and decorative buildings received a notable boost. mid 1930’s some 600 people worked in the quarries. For example, considerable amounts of sandstone Today, some 6.2 million tonnes are quarried, and from Gotland were incorporated in the construction about 350 people are employed in the lime industry of the Royal Palace in . on Gotland.

Lime burning for construction materials purposes has been undertaken since the early Middle Ages. Ini- tially, this was the work of peasants, but in the 1660s the burghers of Visby took over the business; they were known as lime barons and burned lime became an important export. Quarries and lime kilns were

Geotourism highlights of Gotland 41 Geotourism Destinations two very large sea caves have been hollowed out by waves when the sea level of Lake Ancyclus reached up Visby Surroundings to this height. Högklint and Rövar Liljas Håla The lowermost 15 metres of the cliff section below An impressive section of the coast extends from Hög- the reef are composed mainly of marlstone, followed klint, 5 km south of Visby, southwards to Nyrevsudde. by about a metre of crinoidal limestone on which the Högklint itself is 48 m above sea level, one of the high- massive reef complex sits. The reefs were so large and est coastal cliffs on Gotland. The area is also a much heavy that during Silurian time they sank down into visited and well organised . From the the underlying softer sediments. The result can be seen top of the cliff there is a wonderful view over the sea as down-warped limestone beds in the lower part of northwards to Visby and Fridhem. The bedrock consists the cliff face. More reefs extended previously beyond of reef limestone, part of the Högklint Formation. the present shore line, but have long been eroded A steep staircase leads down to a ledge in the cliff, away. An underwater rock shelf stretches away from called Getsvältan (‘Starving goats’). This name comes the beach, then plunging into a steep submarine drop from the fact that at one time goats went down to the in the sea floor. From the top surface of Högklint this ledge to graze, but could not climb back up the cliff underwater cliff margin is clearly visible, barely one again and met a miserable death. From here the reef metre below the water surface. Here and there large structure is very clear, as large irregularly shaped rock scale circular patterns are visible in the sea-bed; these bodies with no bedding planes. High up in the cliff, are known as Philip structures, indicating where previ-

42 Fostering Geotourism on the Central Baltic Islands

View at Högklint from south. Photo: T. Bauert. ous reef bodies were once present and depressed the The cliffs themselves at this point are up to 15 metres underlying sediments, but which have long since been high, consisting of bluish-grey soft marlstone at the eroded away. Essentially, these structures form part an base, with embedded calcareous nodules and thin, ‘underwater map’ of the former extent of Silurian reefs grey, finely crystalline limestone beds. The lowest 3 in this part of the Baltic. to 3.5 metres of marlstone belong to the Lower Visby Högklint lends its name to a stratigraphical unit of the Formation, which are the oldest strata exposed on bedrock sequence – the Högklint Formation, which Gotland. They are succeeded by the Upper Visby For- sits on top of the Lower and Upper Visby formations – mation, which contains more limestone units than the the oldest exposed rock units on Gotland. beds below, and which is more irregularly bedded. The abundance of benthic fossils (animals that lived A signposted path on the tree-covered southern part of on the sea-bed) also increases. Small reef mounds are the cliff plateau leads south to the fishing base of Ygne. present in the upper levels, marking the first appear- After about 800 metres the feature known as Rövar Lil- ance of reefs in the Gotland sequence. The mounds jas håla (‘Robber Lilja’s Cave’) is on the sea-ward slope consist mostly of tabulate corals and stromatoporoids, below the path. It is a cleft inside a part of the cliff with subordinate rugose corals. The marly sediments that has long been falling away, and now stands as a were deposited under fairly quiet water, low energy ‘pseudo-sea-stack’ on the beach. The cleft was named conditions below the wave base in well oxygenated after an escaped villain, Jonas Nilsson Lilja, who in the waters. Upward changes involve less mud units and mid 18th century carried out a series of robberies on more limestones, with more diversified faunas, gener- Gotland and was probably hiding here when he was ally formed in slightly shallower water. Above the eas- arrested in 1753. In the early Spring of 2010, however, ily eroded marly sediments are the more resistant beds most of the stack collapsed and the area close to the of the Högklint Formation, forming the cliff tops and remaining structure is now closed off because of the comprising crinoidal, stratified and reef limestones. risk of further landslide and collapse. This stretch of coast is one of the classic fossil locali- Rövar Liljas håla is also accessible directly from Ygne, ties on Gotland, partly because of the rich faunas from northwards along the beach. This is a popular place the Lower Visby Formation. Large numbers of ‘petri- for a day’s outing from Visby, as can be seen from factions’ were collected from here at the end of the the number of barbecue areas. Högklint forms a fine 19th century by the schoolmaster Mathias Klintberg view to the north. Note the signs that point out that (and presumably his pupils), and they are now pre- the whole area is a nature reserve. This means that, served in the Natural History Museum in Stockholm for example, it is forbidden to deface the rock with and the Museum of Gotland in Visby. ‘Masse’ hammers, chisels or other tools. However, it is allowed to pick up fossils and pebbles that lie freely on the Klintberg was a remarkably versatile and talented man, ground. Here, as along the entire coast of Gotland, best known as a linguistic researcher and documentary please be aware of the overhang below the cliffs photographer, as well as being an avid fossil collector. because the soft, loose marlstone is weathering away The eroded sediments now piled up on the beach are rapidly, so that the rocks are undermined and there is studded with many different types of fossils. Small stro- a high risk of rock falls. matoporoids, tabulate and rugose corals are encrusted

Geotourism highlights of Gotland 43 The pseudo sea stack at Rövar Liljas håla. Photo: T. Bauert. on rock surfaces, and there are many other specimens Snäckgärdsbaden and Korpklint of groups that include brachiopods and gastropods. Of Many of the most interesting geological localities on particular interest are the distinctive coral Goniophyl- Gotland are within walking or cycling distance of lum with its square-shaped form and opening, which Visby. One example is at Korpklint by the beach at in life had an operculum or ‘lid’. Also common is the Snäckgärdsbaden, just north of the town. Also, the beautiful, small ‘button coral’ Palaeocyclus porpita, nearby road cutting on the hill slope leading up from which is a precise indicator of rocks of this age across the Snäck building complex. wide areas of the Atlantic Region as well as Baltoscan- Korpklint is a vertical cliff with a large scree slope on dia. Among the brachiopods, Eoplectodonta transver- which large boulders have tumbled down towards the salis is common and readily recognised with its con- road and beach. Over 20 metres high, the cliff is a cavo-convex shell, generally preserved in a brownish beautifully preserved section through the Upper Visby colour. ‘Index fossils’ such as these are important tools and Högklint formations. The lower beds, about 5 for correlating beds from different localities. metres thick through the Upper Visby Formation, com- Small, loose fossils here are found most easily in the wave-washed pebbles, and the best rewards come Swimming by Snäckgärdsbaden, Visby in the early 1900 from sitting calmly in one spot to sift through the (top photo on right page). Photo G. Heurlin. View towards the north showing the Upper Visby Forma- material – which is far more comfortable than walking tion (lower part) and Högklint Formation (topmost). Photo along with a bent back and peering at the ground! S. Willman.

44 Fostering Geotourism on the Central Baltic Islands Geotourism highlights of Gotland 45 prise bluish-grey marlstones with irregular calcareous Lummelundsbruk and Lummelunda Cave nodules and thin beds of brownish grey, fine crystal- Energy from the rapidly flowing water of the river line limestones. The sequence is highly fossiliferous. Lummelundaån was once the basis for industrial Högklint rocks at the top of the section are difficult activity at Lummelunda, including a textile mill, to access, but there are many boulders on the slopes paper mills and sawmills. From the late 17th century below the cliffs. until 1712, five water wheels provided the power The Högklint rocks in the cliff are thick-bedded, light for an ironworks, using iron ore from Utö in the grey, fine to medium grained crinoidal limestones. . One of these waterwheels, Common fossils are stromatoporoids, corals, bryo- Överstekvarn, is preserved today. Around the river zoans and brachiopods. Many of the fossils are frag- there are still traces of the industries in the form mentary and worn, indicating transportation in the of slag heaps, ruins of buildings, remains of roads, high energy reef environments. and bridges. In the late 19th century the digging of Beds of the Upper Visby Formation are best exposed drainage ditches around mire, from where and accessible in the road cutting ascending the hill the water came, made it impossible to continue the from the beach, immediately south-west of the hotel industrial activities when the water flow in the river complex. This section is extremely fossiliferous. There decreased dramatically. are three small reef knolls in the section, which are Martebo mire was formerly one of Gotland’s larger easily recognised and accessible for close study; fossils bog areas, most of which are now drained and con- are very common around the reef margins. The most verted to croplands. Water ran from the bog through common fossils are tabulate and rugose corals, stro- matoporoids, gastropods and brachiopods. Dripstones at the Lummelunda cave. Photo H. Reintz.

46 Fostering Geotourism on the Central Baltic Islands underground cracks to form the rapidly flowing cal dissolution of the underlying limestone. The path stream, which then carried on downslope before then leads further along the beach ridges formed dur- emerging through a beach cave at the foot of the ing Ancylus times. The largest and highest ridge, the cliff. Although no longer a source of industrial power, ‘Ancylus wall’ marks the level of the highest water the river is still important in many ways, including a surface of Lake Ancyclus, where it stood for an exten- breeding location for sea trout. sive time before the lake waters regressed. The main

In 1948, three curious teenage boys managed to road 149 from Visby runs along the level of this beach creep inside the beach cave along the outlet stream, ridge. and discovered the passage into a very large cave From the lookout point on the cliff edge, with its mar- with stalactite formations. This cave was formed prob- vellous views, a staircase then leads back downhill. ably before the last Ice Age, eroded and hollowed out In the cliff walls there are several beach caves, carved by the carbonate-rich water that flowed through the out by waves in former times when the sea reached to cracks in the bedrock, and which dissolved the cal- this level. At the base of the cliff there is a lush decid- cium minerals in the rocks. When the water, saturated uous wood. The rich vegetation is a result of the fine with lime, dripped down from the roof of the cavern, nutritional sediment, now as soil, that was deposited the calcium carbonate built up as beautiful stalactites on the sea-bed in earlier stages of development of and stalagmites. the Baltic Sea, and which is kept moist constantly by

Parts of the cave were opened to tourists in 1959 after the water flowing through cracks into the springs and a new entrance was blasted open. Since then, spe- stream of Lummelundaån. Here and there are eroded leologists have penetrated further and further into the gutters, which drain off waters from the springs and cave system, and as of now approximately 4 kilome- shallow wells during periods of high flow rates. tres have been mapped. A small current of water still flows through the active part of the cave, and after the spring snowmelt it can sometimes reach former Northwestern Coast flow volumes, making it impossible to visit. However, Lickershamn throughout the summer the cave is open to tourists, and in one of the outside barns there is an exhibition Lickershamnsviken is one of the bays of the north- with information on the geology of Gotland in gen- west cliff coast that was formed originally as an ero- eral and karst caves in particular. sion valley. Rivers and glaciers eroded weak parts of the cracked cliff bedrock. Thus, the coastal cliff turns A nature trail starting from the mouth of the tourist inward toward the land here and appears in the bay cave leads upwards to the cliff top. Here the ground as an inland cliff. Sediments have accumulated in the is uneven because of the shape of the reef bodies in bay and now fill a large part of the ravine. the underlying rock, but also because there are many sinkholes in the area. Sinkholes, or dolins, are fun- Naturally, post-glacial erosion has also affected the nel shaped pits in the ground, resulting from collapse area. The inland cliff on the west side of Lickershamn of the bedrock because of undermining by chemi- valley is highly eroded by forces of the sea and there

Geotourism highlights of Gotland 47 48 Fostering Geotourism on the Central Baltic Islands

Jungfrun at Lickershamn is the largest sea stack on Gotland. Geotourism highlights of Gotland 49 are a large number of sea stacks, either in smaller level. On the sloping shelf between these cliffs there groups or in large sea-stack fields. The sea stack field, is a series of well developed sea walls. A creek that which lies just to the left of the road down to Lick- drains Sågvätar, a wetland area a few hundred metres ershamn, is worth visiting. The stacks here look very inland, cuts deeply through the rock before it runs out strange where they protrude from the surrounding at the beach. The stream dries out in summer, but the green vegetation. water flows rapidly during winter and spring. Further out on the coast to the west of the harbour the At several places on and below the cliff, calcareous steep coastal cliff is again present. The cliff exposure tuffs are deposited. These are related to groundwa- displays the same bedding sequence as in Ireviken, ter seeping from the cliff at specific levels. The lev- and it also contains essentially the same fossil fauna. els coincide with bentonite beds within the layer At the base there are thin-bedded marlstones of the sequence. Bentonite is volcanic ash that has been Lower Visby Formation, followed by the slightly more deposited as a clay. The clay swells up when it is wet, calcareous marlstones of the Upper Visby Formation forming dense layers. As a result, water flows within and limestones of the Högklint Formation at the top. the cliff onto the top of the bentonite layers and down The sharply protruding cliffs of Jungfruklint and Stuk- to the beach on the cliff wall. Flush fen plants like lint are Högklint reefs. The reef limestone is more bird’s-eye primrose and the lily Tofieldia calyculata resistant to erosion by the sea and ice than the bed- often grow where the water seeps out. ded limestone in between. The area around Jungfruklint and Stuklint is a nature The cliff reaches its maximum height, 27 metres reserve. above sea level, at Stuklint. The only remains of the reef in Jungfruklint is a very large, high sea stack, Ireviken known as Jungfrun (the Maiden). It is the largest sea stack on Gotland, 26 metres above sea level and 11.5 Ireviken is one of the deep bays on the north-west metres above the ground. The name derives from the coast, interrupting a long stretch of high cliffs and tragic tale of the virgin Öllegård and her beloved, a with a long, sandy beach. The coastal cliff here story you can read more about on the information turns inland, forming a ravine filled with sediments. board. The sea stack has been sculptured by the Through the valley runs the Ireån stream, which waves of the Littorina Sea, 6 500 years ago. The north drains Tingstäde lake and Elinghems bog. It cuts deep side of Jungfrun is almost flat as it comprises one wall into the valley sediments that were deposited origi- of an old vertical crack; the opposite wall has col- nally as beach sediments and drifted sand. The sand, lapsed down onto the beach. On its landward side is gravel and shingle were deposited during Littorina a shallow beach cave. Below the cliffs there is a great time. The inner parts of the bay are lined by cliffs accumulation of collapsed rocks, many of which are with beautiful abrasion formations such as sea stacks, unusually large. beach caves and niches, all formed by waves during Southeast of Jungfruklint the cliff is divided into an the maximum level of the Littorina Sea. outer, lower coastal cliff, consisting of marlstone, From the fishing hamlet on the south-west side of the and an inner limestone cliff on the higher 25-metre bay, follow the coastal cliff southwards. There are four

50 Fostering Geotourism on the Central Baltic Islands high, protruding and overhanging cliffs, Tretrivsklint, At one point along the lower part of the section, there Millingsklint, Gaituklint and Snipklint, each compris- is a colony of the tabulate coral Halysites, about 100 ing enormous reefs. There are also many large boul- metres long, although much of it is often covered by ders that have fallen onto the beach. These reefs rep- beach shingle. On this reef there are also specimens resent contemporaneous reef structures that largely of the rugose coral Cystiphyllum in their original ran parallel with the coastline. growth position. Note the root-like appendages on these corals. They can also be found in the form of The lower part of the cliff, mostly between the reef small, loose ‘twigs’ in the fossil material eroded from masses, is 24 metres high and consists of soft, highly the marlstone. It is very important that this reef should fossiliferous bluish-grey marlstone. It is thin-bedded not be destroyed by chipping off fossils and hammer- with irregular nodules and beds of fine-grained lime- ing the cliff. The erosive forces of the waves, ice and stone. These beds are part of the oldest exposed rocks rain are beyond our control, but if you wish to collect on Gotland. The lower 9 metres belong to the Lower fossils, take advantage of this erosion and only take Visby Formation. The boundary to the Upper Visby loose-lying corals. Formation, which is about 15 metres thick, is in the middle of the section, 13.5 metres above sea level. The Lower Visby Formation is comparatively fossilif- The boundary is difficult to identify without detailed erous. The small ‘button coral’ Palaeocyclus, and the study of the fossil fauna, but it is roughly at the level brachiopod Eoplectodonta transversalis occur only in where the scree slope is succeeded by the vertical these beds, and are used as index fossils to correlate cliff, because the Lower Visby Formation are more contemporaneous sediments throughout the world. argillaceous, making them softer than the Upper The Upper Visby Formation has an extraordinarily Visby Formation, whose higher content of limestone rich fossil fauna, dominated by corals, brachiopods has produced a vertical profile. and bryozoans, although stromatoporoids, gastro- Especially after recent rainfall, a sharp horizontal pods, ostracodes and trilobites are abundant, whereas boundary is visible between the dry upper part of crinoids, bivalves and cephalopods are sparse. Lime- the cliff, and the damp lower part of the marlstone. stone beds are more common higher up in the Upper This is because of the presence of a bentonite bed. Visby Formation, where there are also small reef A bentonite is a thin layer of clay that was deposited knolls. originally as volcanic ash on the sea floor. Bentonite The Högklint Formation rocks at the top of the cliff clay swells on contact with water, making the hori- are dominated by limestone with isolated, massive, zon impervious, so that groundwater cannot perco- dense reefs at intervals of several hundred metres. The late through it, but flows out at the bentonite bed and reefs consist mainly of stromatoporoids and tabulate then runs down the cliff face. At least three such ben- corals, but also of bryozoans, crinoids and calcare- tonite horizons are present in the lower part of the ous algae. Coarse fragmental limestones, made up of section. The bentonite beds are easily traced, because crinoidal fragments, occur on the sides of the reefs. their upper surfaces are aquifers and the percolating These are succeeded gradually by fine-grained strati- water gives rise to a border of herbaceous plants. fied limestones further away from the reefs. Reef, frag-

Geotourism highlights of Gotland 51 52 Fostering Geotourism on the Central Baltic Islands

The Snipklint at Ireviken, NW Gotland. Geotourism highlights of Gotland 53 mental and fine-grained limestone can all be studied December. Birds also thrive by this river, and dippers more closely in the scree on the beach. live off the insects at Ireån. Because of the steepness of the cliff, the reefs are dif- ficult to access, but there are many large boulders of Bläse Limeworks Museum reef material on the beach. The reefs are surrounded The lime industry has left its mark on northern by a well-bedded limestone-marl alternation. Gotland. Old quarries, lime kilns, lime warehouses Ireviken is one of the most fossiliferous localities on and heaps of waste products are spread along the Gotland. Because the cliff erodes at an annual rate of entire coast. Quarrying and lime burning have been about 1.5 cm, new material is exposed constantly. In undertaken since the Medieval Period, and on an addition to fossils, the glittering, golden, cubic crys- industrial scale from the 17th century, when the tals of the mineral pyrite (iron sulphide) are common farmers no longer were allowed to burn lime and the here. In some cases the calcite in the fossils has been businesses were taken over by the burghers of Visby. replaced by pyrite, which unfortunately corrodes eas- The large wooden-fired lime kilns demanded huge ily, partly due to its iron content. amounts of fuel, and as early as in the 18th century, the surrounding woods were almost all cut down, At some places along the cliff, where the water slowly leaving a barren landscape. During his trip to Gotland trickles out, calcareous tufa is being formed. The cal- in 1741, Linnaeus noted that in : cite-saturated water deposits calcite on the moss that grows on the ledges. The greyish calcareous covering There is enough fuel here, but the wood is uneven in feels hard and crisp, and gradually, when the actual quality; if the lime-burners are allowed to do as they please with the woods, this part of Gotland will soon moss has decomposed, it will leave an impression – a be cleared of forest, since for every 2 days’ burning, type of modern fossil-formation. 20 fathoms of firewood are used. The marlstone in Ireviken has been the subject of Bläse Limeworks is situated on the east side of Kap- many extensive studies of the evolution and extinc- pelshamn bay. Lime has been burnt here since the tion of different animals. These studies have pro- late 19th century, with production continuing until vided data for theories on global cyclic changes in 1945. The works, together with the harbour, two coal- the oceans, and their impact on sedimentation. The burning lime kilns with huge chimneys, and the lime ‘’ is the established name for a minor warehouses now form a museum of the stone indus- that occurred all over the world dur- try. During its days of glory in the 1920s and 1930s, ing this time. about 140 men worked at Bläse. An entire community The area around Ireviken bay has a number of grew up around the works. The quarry from which the in beautiful surroundings, an old mill setting, and a limestone was taken is situated 2 km north-east of the pleasant bathing beach. The old mill once belonged works. The railway line to the quarry has been restored to Ire farm, dating back to the 16th century. Red hel- and tours with the ‘Stonetrain’ are popular among vis- leborine blooms around the bay in summertime. itors. The museum also offers demonstrations of the In autumn sea trout migrate up Ireån, and fishing is lime-burning process, and there is an exhibition por- therefore prohibited between 1st October and 31st traying the life of the former workers.

54 Fostering Geotourism on the Central Baltic Islands The coal kilns at Bläse were shaft furnaces for con- Fårö tinuous burning. Limestone and coal were packed in Digerhuvud at the top and the burnt lime taken out at the bot- The largest continuous sea stack area of Gotland, and tom. The burnt, unslaked lime, was put in storehouses of the whole of Sweden, is along the north-western where it was then slaked; i.e. water was added, coast of Fårö. It is called Digerhuvud; there are park- reducing it to white, powdery slaked lime. In modern ing spaces and explanatory sign-boards on the road- times the lime is slaked in the big silo. side above the localities. From a cliff composed of The older, wooden fired kilns were stoked at the reefs belonging to the Hangvar Formation, waves base, and limestone was stacked on top. The kiln and water currents have carved out several hundred was closed and the lime then burned for three to stacks. The area of the sea stacks extends from Släthäl- four days. When firing was complete and the fire lar in the south-west to Helgumannen fishing base in was extinguished, the lime was removed to the ware- the north-west. It is 3.5 km long and on average 50 houses where it was slaked. A kiln of this kind, built metres wide. The sea stacks were formed during the in the mid 18th century, is preserved near the old post-glacial regression, when elevation of the land limestone quarry. gradually exposed the rock surface. The stacks stand-

‘Stonetrain’ at Bläse Limeworks Museum. Photo: T. Bauert.

Geotourism highlights of Gotland 55 ing in the water are still influenced by the erosive remaining cliff along the landward side of the sea forces of the waves. The limestone plateau from which stacks. the lowest sea stacks are carved forms an underwater cliff, dropping vertically down to 50-60 metres under Avanäset water. Outside the cliff edge, strong underwater cur- Travelling towards Avanäset on north-eastern Fårö, rents can be formed during certain wind conditions. there is a noticeable and quite abrupt change in land- Please beware that these can be extremely dangerous scape vegetation. Whereas limestone bedrock and for swimmers. sea walls of shingle dominate the rest of the island, The sea stacks consist of reef limestone, dominated by this region has a deep sandy soil, with hardly any stromatoporoids which are the most resistant fossils, limestone bedrock exposed. Only at the beach to the although there are also corals that include colony- south-south-east of Holmudden lighthouse are there some low sea stacks. Sand dunes form smooth land- forming rugose and tabulate forms. Remains of sea forms and a sand pine forest covers the inner parts of lilies (crinoids) that accumulated along the flanks of the area. The ground is covered with mosses, lichens the reefs are also present at places in the limestone. The closely standing sea stacks vary in size up to Sea stacks at Digerhuvud consist of hard, weather-resistant reef rubble limestone (above). M. G. Bassett pointing at cross­ 8 metres high. The ground is otherwise covered by bedded fossiliferous limestone which represents high-energy beach ridges of shingle, which also covers part of the channel deposits between reefs.

56 Fostering Geotourism on the Central Baltic Islands Geotourism highlights of Gotland 57 58 Fostering Geotourism on the Central Baltic Islands Langhammarshammar The contemporary reefs forming the sea stack area at Digerhuvud are also preserved at Langhammars- hammar on the northernmost peninsula of Fårö. A narrow road that meanders through a bleak, barren landscape of shingle banks with low-growing wind- swept junipers, leads to a beautiful sea stack area on the beach. From the landward cliff edge the ground slopes out into sea. Here there are 70 – 80 sea stacks, with heights up to 10 metres. Many are pillar shaped and stand majestically and closely grouped on the beach. They are among the most impressive and spec- tacular rauks on Gotland, and Langhammarshammar is without doubt one of Gotland’s biggest attractions.

Geotourism highlights of Gotland 59 and vascular plants such as heather, blueberry and Another reserve, at Ulla Hau, located further west lingonberry, uncommon in the rest of Fårö, typical of in the middle of the narrowest part of the tongue, lime-poor soils. In depressions between the dunes, consists of a giant horseshoe-shaped sand dune. The small bogs have been formed bordered by alder, a opening of the horseshoe faces to the north. From the rare species elsewhere on Gotland. The bogs are inside of the horseshoe, forming a deflation surface affected by acidic water, which has resulted in the some 1.3 km wide, the sand is blown by the wind, formation of a wetland environment which is unique transported to the south and deposited on the dune for Gotland. Here, there are peat mosses (sphagnum), which is up to 15 metres high. This dune probably crowberries and common bog-sedge, which are typi- formed already in 18th and 19th centuries as a result cal species in such acidic bogs. of high-intensity land use. In order to prevent the dune The nature reserve at Skalahauar is a large sand-drift wandering migrating southwards, pine and sand-bind- field located on the south-eastern area of Avanäset. ing grass were planted during the early 20th century. The dunes are high and make the landscape hilly and Now the sand dune is covered largely with pine for- undulating. The drifted sand area probably accumu- est. In this environment, with open sandy areas, an lated in the 18th and 19th centuries, when land clear- ancient pine forest and a particular local climate, ance from logging and intensive pasture development there is an interesting insect fauna in which many rare allowed the wind to push the sand freely across the species thrive. Ripple-marks (small ridges formed by area. Now forests again cover most of Avanäset. wind) are common on the open sand surfaces.

60 Fostering Geotourism on the Central Baltic Islands

Sand dunes at Ulla Hau, Fårö. Photo: T. Bauert. The sand deposits of Avanäset were deposited by the From the coast there is a spectacular view of Bun- glacial rivers that flowed through cracks and tun- genäs in the furthest distance, and of the isles of nels in the glacier during the deglaciation phase of Skenholmen and . The landscape at Lergrav the Weichselan ice. They are part of the same gla- is barren, but the environment is favourable to spiked ciofluvial deposits that form Gotska Sandön, and are speedwell, common rock rose, Vincetoxicum and exposed parts of a 120 km long ridge of sand, gravel moon carrot. and till that stretches from Klints Bank to the east of South-east of Lergrav is the island Furillen, where Gotland north, over Salvorev north-east of Fårö, and limestone was quarried and shipped out from the to the shallows of Kopparstenarna 20 km northwest beginning of the 20th century until the 1970s. The of Sandön. abandoned lime factory has now been transformed into a fashionable hotel and restaurant. A large part of Northeastern Coast the island is a bird protection area during the breed- On the north-eastern coast of the island is the only ing season. The island is so close to the coast that it archipelago displayed on Gotland. From the coast of can be reached by car via a road running along a spit. Bungenäs to Slite there are a dozen small islands. The coastline is lobate, with many deep bays and protrud- Kyllaj ing headlands. Land topography is often hilly because Kyllaj is a village and an old harbour built around of the reef limestone in the bedrock. Stratigraphically, the former lime industry on the eastern coast of the this bedrock is part of the Slite Group, which apart parish of . From the edge of the hillside there is from reef limestone, includes bedded, pure limestone an astonishing view over sea stacks, limestone ruins, and occasionally marlstone. Limestone has been harbours, the sea, and the archipelago with its isles of quarried in the area for centuries, and lime indus- Klasen, Fjaugen and Lörgeholm. tries, primarily the burning of limestone, have been intense. Traces of these activities, in the form of the The stone and lime industry developed during the many quarries and lime kilns, are a distinctive feature 17th century. Limestone was quarried in the surround- of the coast here. ing region, then taken to the kilns on the hillside and burnt. The burnt lime was stored in warehouses by the harbour, where it was slaked with water and then Lergrav packed into barrels. The lime was shipped on small The nature reserve and fishing base of Lergrav lies cargo boats to harbours along the Baltic Sea coast. between the bays Lergravsviken and Valleviken. In Limekilns close to the cliff comprise remains of the the 800 metres long sea stack field below the eastern earliest kilns, together with well-preserved 19th and cliff of Lergravsberget, one of Gotland´s most remark- early 20th century kilns. able sea stacks, Lergravsporten, is preserved. It is an arch-shaped sea stack through which many visitors On the hillside at Kyllaj, facing the sea and sur- enjoy running. Madonnan med barnet (the Madonna rounded by grassland, there are many beautiful sea with child) is another popular high sea stack, named stacks. These were sculpted by the waves of the Lit- in relation to ancient folklore. torina Sea, about 6500 years ago. When Linnaeus

Geotourism highlights of Gotland 61 62 Fostering Geotourism on the Central Baltic Islands Geotourism highlights of Gotland 63 Lergrav rauk field overlooking Lergravs- viken bay in northeastern Gotland. was here in 1741, he made a com- pletely accurate description of the sea stacks and the formation of them, although he had no knowl- edge of inland ice and isostatic land elevation. In his travelog he wrote: We called the ‘Stone Giants’, as had the learned bishop G. Wal- lin, that which we saw by the sea near to Kyllaj: between the customs officer’s house and the lime kiln of Kyllaj there was a slope towards the sea where stood many high and thick limestone rocks 4-6 fathoms (8-12 m) high, arranged in a row like the ruins of churches or castles, of which those standing at a lower level of the slope were taller than those higher up, so that the heads were all at the same level. From a distance they looked like statues, horses, torsos and I do not know what kind of ghosts. Evidently, this had been formerly a limestone mountain, the roots of which had been ground, cut and formed by the heaving waves of the sea, till it finally left these Lime kiln remains at Kyllaj, northeastern Gotland. stones in their present form; there is no doubt that the water that has cut into the sides of these cliffs and (the Beach Rider), was a customs officer who had the made them narrow at the base has also been able to task of guarding the coast and the harbour. Strandri- cut away and erode the earth between them. Stone dargården is now owned by the Bunge Museum and giants of the same size were seen all the way along is open for visits during summer. the road to Slite. From the beach, probably sitting on a pier, Linnaeus The old house Strandridargården was built in the was able to see all the sea stacks and the house. A 18th century by the customs officer Johan Ahlbom, a woodcut, made after his artwork, is included in the former warrior in King Karl XII’s army. Strandridaren published travel log from 1745.

64 Fostering Geotourism on the Central Baltic Islands St. Olofsholm scenery.

Some of the raw material from this industry is from are 5-6 metres high. On the southern slope, in the the nearby limestone outcrop, Kyllaj hajdar – a flat, central area are single small stacks. In the western treeless landscape. Scattered around are small, shal- area there are several large old limestone quarries. low limestone quarries. Grazing animals have long shaped the landscape and today the area is open moorland with grass and low

St Olofsholm junipers. Here and there spruce, pine and white beam are growing. The southernmost headland in Hellvi parish is named St Olofsholm, which is a hill of reef limestone; in According to the legend of Olaf the Holy, the Norwe- prehistoric times and in the Middle Ages this was an gian King Olaf Haraldsson came ashore at Akergarn island, called Akergarn. The area south of the old har- (St Olofsholm) during a trip to Russia in 1029, and bour on the eastern coast is a nature reserve. Here then converted the Gotlanders to Christianity. Up on the limestone slabs are partly visible and descend the hill are the remains of a chapel, St. Olaf’s church, in wide steps towards the sea. The slopes of the hill built in medieval times in memory of this alleged are covered by sea walls, and a low cliff runs along landing. According to legend, Gotlanders were bap- the eastern shore. Along the beach in the north-east tised in ‘St. Olaf’s vaskefat’ (St Olaf’s wash-bowl), a there are 15 sea stacks, many of which are high out of depression in one of the sea stacks just south-west of the water on the washed rocks. The largest sea stacks the chapel.

Geotourism highlights of Gotland 65 Gotland’s first lime kiln was erected on St Olofsholm Northern Inland in the early 17th century. Gotland belonged to Den- Tingstäde – Hejnum area mark at the time and it was the Danish King and a Tingstädeåsen is a ridge situated 10 km west of Slite. company called Gullandska Compagnie, that were It is one of very few and the largest esker on Gotland. behind the enterprise, with the intention of produc- An esker is a glaciofluvial deposit, formed by a melt- ing lime for export. The activity was continued until water stream inside a tunnel or crack in the glacier. 1860. In 1901-1953, blocks of stone were quar- It consists of sorted sand, gravel and stones. Ting- ried on a large scale. A harbour with a quay made städeåsen reaches a maximum height of 12m and a it possible to export the limestone further. Wagons length of 12 km. It extends from south-west to north- on rails were loaded with limestone, and the loads east on the northern side of the lake Tingstäde träsk. were transported to the quay and tipped directly into The lake, which is the second largest on the island, is the holds of the boats. In 1953 the limestone quar- dammed by the esker, making its water level higher rying was moved to Storugns in Kappelshamnviken compared with the ground level north of the ridge. on north-western Gotland. Traces of the limestone Some people have interpreted Tingstädeåsen as a quarrying can still be seen in the surroundings of terminal moraine, formed parallel to the ice margin St Olofsholm. during a period with little or no melting. However, eskers are always extended along the ice movement St. Olofsholm: view at adjacent Ytterholmen island. direction.

66 Fostering Geotourism on the Central Baltic Islands Southwards from the lake runs the valley of Hejnum is covered partly with thin layers of till or weathering parish. From the parish church towards the north- soil. Open pine forest alternates with treeless areas, west there is a dirt road across some hilly fields. The where only dry-hardy vascular plants, mosses and elongated hills are parallel land forms interpreted as lichens grow, together with scattered juniper bushes. drumlins, which are types of moraines formed dur- Sheep and cattle have grazed here for long periods ing the expansion of the glacier. They extend in the of time, keeping the woods and rocky ground open. same direction as the ice movement. Part of the agri- The white stonecrop, with its red, bulb-shaped leaves, cultural lands in the valley, were former wetlands which store water, brings colour to large areas of that have been drained. The valley is lined with pre- the rocky ground. In June it blooms with white and historic settlements and burial grounds. East of the pink flowers. Another creeping plant growing on the valley, Hejnum hällar and File hajdar, is the largest shallow soil cover is the Gotlandic variety of rock- continuous stretch of flat limestone outcrop/alvar rose, which in Sweden is present only on Öland and area on Gotland. If you turn eastwards towards the Gotland, and here rather rarely. It has needle-shaped nature reserve Kallgateburg, from the road between leathery leaves, also adapted to the dry climate. Its Tingstäde and Hejnum, you will pass part of the area yellow flowers shine brightly in the June and July before you reach the reserve itself. morning sun. File hajdar also hosts the largest popula- The bedrock of the rocky ground consists of pure, tion of Easter pasque flower in Scandinavia. Its large, hard limestone which belongs to the Slite Group. It light purple flowers bloom in April-May.

Geotourism highlights of Gotland 67 68 Fostering Geotourism on the Central Baltic Islands Pine and juniper are prevalent in the forest, although spruce, oak, yew and white birch also occur. The eastern edge of the rocky area is inter- sected by ravines that were eroded by glacial rivers in the melting inland glacier. Here is a border between areas of different bedrock. To the north and west are File hajdar and Hej- num hällar, the higher extensive areas of pure limestone, while the lower, muddy areas on marlstone ground at Hejnum Kallgate are to the east and south-east. On the slope, there are several springs and brooks, created by emerging subsoil water, which has infiltrated through cracks in the limestone. The water flows over the muddy, slightly sloping area and a special wetland, a flush fen/spring mere, is formed. This fen is called Rövätar. The calcareous, cold and constantly moving water has given rise to a very distinctive flora, with species such as brown bog-rush, broad-leaved cottongrass, blunt-flowered rush, birdseye primrose, but- terwort, alpine butterwort, great sundew and Pugsley´s marsh orchid. Rövätar is damned to the east by a major shingle beach ridge, Kallgateburg, which was formed during the Ancylus lakes high- est water level 8000 years ago. On top of the ridge runs the former main road from Fårösund to Visby – Kallgate (Charles’ road), now visible as a broad path. Here grows one of the largest yew populations in the country. East of the ridge is Hejnum Kallgate. This area is particularly popular among day visitors in Hejnum hällar alvar. early June, when the lady´s slipper orchid is in bloom.

Geotourism highlights of Gotland 69 Eastern Coast The strata exposed in the upper part of the beach Gothemhammar and in the low cliff belong to the upper Klinteberg and Halla formations. They are mostly thin-bedded, The headland of Gothemhammar to the north of commonly penetrated by trace fossils. The rocks con- Botvaldevik in , eastern Gotland, is reached sist mainly of nodular and laminated argillaceous via a poor gravel road that runs along the coastline limestones, interbedded with softer, bluish-grey from Åminne to Botaldevik. From Åminne, turn off marlstones. Fossils are very common at some levels, towards the road marked to Gothemhammar and including numerous brachiopods, trilobites, bivalves, drive through the cottage area past the small fish- gastropods, tentaculites, bryozoans and ostracodes. ing base of Bryggan. Park by the information board. Calcareous algae, up to several centimetres across, After a short walk along the beach to the east you will are abundant. One bed is covered completely with come to some low cliff sections. The beach itself is the bivalve Modiolopsis. made up of shingle banks, which change from year to year because of wave action. This also means that The boundary between the Klinteberg and Halla for- the exposure of the rocks also varies from one year mations is clearly visible in parts of the section, as a to another. geological discontinuity between the two rock units.

Shallow coastal cliff at Gothem- hammar. Photo: T. Bauert.

70 Fostering Geotourism on the Central Baltic Islands A discontinuity indicates that the sequence of rock The cliff here is about 20 metres high, comprising layers is not complete, but that a layer representing reef limestones with abundant stromatoporoids and a certain period of time is either missing or not fully crinoidal beds. Between the foot of the cliff and the represented, because of a gap/long interruption in sea there are huge fallen boulders, in which stromato­ sedimentation. The original surface may have been poroids are preserved in their position of growth. All just above, or just below, sea level and subjected to the rocks here belong to the Hemse Group. The strati- erosion by currents and waves – so that there is a fied limestones, which are also clearly visible at the gap in the record of sediment deposition. During this water’s edge and under the sea itself, are about 15 interval, sediments on the sea-floor may have become metres thick, bluish grey in colour with argillaceous lithified as ‘hardgrounds’ on which various burrowing beds and are quite thinly bedded. Many fossils from and boring organisms were active. these beds can be found in the shingle and gravel on Strata immediately overlying the discontinuity surface the beach. are developed as thin marlstones with common and Probably nowhere else on Gotland is there such an well preserved brachiopods and trilobites. These beds abundance of fossil molluscs, with regard to both indicate a reintroduction of marine sedimentation. the number of individuals and the number of spe- Above the beach, alpine blackberries carpet the cies. Of particular note is the profusion of the bivalve ridges, succeeded at higher levels by coniferous forest Illiona prisca, whose characteristic features include and where the landscape rises as a cliff. Higher up, its smooth, brownish shell surface. The numerous at about 12 – 15 metres there are remains of a . straight orthoceratid cephalopod shells preserved in Such forts may have served as fortified settlements rocks near the water’s edge are almost all pointing in in times of unrest, but could have also been used the same direction. This indicates that sometime dur- as trade centres, for rituals, and as courts (Tings) in ing the Silurian Period, the floating empty shells from peacetime. What remains today is a 500 metre long rampart, running completely across the highest point dead animals were aligned by waves/current action of the promontory. and then embedded in the sediment in that position. Other fossils such as brachiopods, ostracodes and tabulate corals are also very common. Grogarnshuvud Among the pebbles on the upper of the two beach By contrast to most of the east coast of Gotland, ridges are some fossils preserved in a different texture, which is quite flat, the area known as Östergarns- landet is quite different in having limestone hills. The and which are also notably different to the touch. easternmost headland on the hill is These are mostly tabulate corals, especially Syrin- named Grogarnshuvud. From Katthammarsvik there gopora and Favosites, and they come from a bed of is a signposted gravel road towards Grogarnsberget; silicified rock. The original calcite skeleton in these follow the road for about 2 kilometres. At a fork with fossils has been replaced after the animal died by the a sign to the right uphill to Grogarnsberget itself, take harder silica mineral quartz, which was introduced the left fork instead which leads to the beach at the into the sediment in the form of volcanic ash and dust locality of Grogarnshuvud. from nearby volcanic eruptions.

Geotourism highlights of Gotland 71 Cliff at Grogranshuvud.

72 Fostering Geotourism on the Central Baltic Islands At the harbour in Katthammarsvik is an exposure on there is a small road running uphill and then towards the rock surface by the beach, just to the right of the Kuppen, the easternmost part of the peninsula. Where jetty at the far end of the car park. Here there is a the road reaches the shore it forks, and the northern deposit formed almost entirely of accumulated shells fork leads to an old restored navigation beacon where of the large bivalve mollusc Megalomus gotlandicus, there is room to turn and park. and which gives its name to the bed of rock itself. From Kuppen northwards the beautiful coastal cliffs This bed lies immediately below the exposed beds are very well exposed. The cliffs extend for several at Grogarnshuvud, and forms the base of the Hemse hundred metres back towards Herrvik. They are Group in the north-eastern area of its outcrop. formed of spectacular stromatoporoid reefs consist- ing of large, non-framebuilding stromatoporoids. The reefs grew on a broad, shallow-water carbon- Kuppen and Snabben ate platform. A high-energy environment is indicated The Östergarn peninsula is characterized by sev- by abundant coarse-grained fragmental limestones, eral low, undulating hillocks composed of stacked eroded surfaces, and abraded boulders. On the shore stromatoporoid flat reefs and interbedded coarse- immediately opposite the car park, the low cliff Snab- grained limestones. Stratigraphically, they belong to ben preserves spectacular exposures of the laterally the Hemse Group. From the fishing hamlet at Herrvik extensive bedded stromatoporoid reefs, with evi-

Geotourism highlights of Gotland 73

Coastal cliff at Kuppen. dence that karst surfaces and sea stacks were devel- hamn, there is an example of a special landscape, oped during Silurian times. which was influenced very early by man. A cattle The sea has undermined the cliff all along this coast, path, lined with dry-stone walls, leads from the park- dislodging enormous boulders which have then slid ing place to an open, flat and desolate moor where down to the water. The shores southeast of Kuppen there are eight scattered giant Bronze Age cairns. consist of shingle beach ridges alternating with sandy Uggarderojr is the name of the largest cairn. With its areas. From this part of the coast there are fine views 45 metre diameter and almost 8 metre height, it is the across to the small island of Östergarnsholm, which largest cairn on Gotland. is also made up of Hemse stromatoporoid reef lime- Bronze Age cairns are graves, built in prominent stones. places along the coasts and fairways, probably form- ing landmarks, and demarking territory. Today, the surrounding land area is about 7 metres above sea Southeastern and southern Coast level, and since the land has risen by about 2 metres Uggarderojr per thousand years, the shoreline must have been 6 The south-eastern coast area of Gotland, with its bed- metres higher in the mid-Bronze Age, three thousand rock of soft marlstone, is a very flat lowland, sloping years ago. This means that the cairns here must have gently towards the seashore. At Uggarderojr, a few been built immediately adjacent to what was then the kilometres from the coast to the south-west of Rone- shore.

74 Fostering Geotourism on the Central Baltic Islands The surrounding area is now quite void of stones, but Holmhällar before the cairns were built, great quantities of boul- Holmhällar is the furthest headland on the south- ders and rocks from the rocky moraine cover must eastern coast of Gotland. From the car park at the have covered the ground. The rocks were then used boarding house it is a short walk to the beach via as building material for the cairns. Further away from a long dirt track. On the beach there is a sea stack the cairns, for example on the coast north of Hus fish- field with stacks that are somewhat different from ing base, there are examples of areas still rich in a others on the rest of Gotland. But as elsewhere, the cover of rocks and boulders. stacks, or raukar, are limestone formations, that have Only a few Bronze Age cairns on Gotland have been remained standing after the sea eroded the weaker excavated, but inside the cairns are found dry-stone rock surrounding them. They often comprise original walls, stacked towers, coffins of limestone slabs parts of reefs, since reefal limestones are the hardest (cists), and other building structures. The cairns often parts of the limestone bedrock. contain burials of more than one person, and they The sea stacks at Holmhällar expose a very special were used over a long period of time. Later cairns, reef type. The characteristic form is that of an atoll- built during the Iron Age, are often smaller than the like semicircle open to the north-west and with dis- Bronze Age cairns, and are often gathered together tally dipping reef surfaces. By analogy with similar into larger grave fields. structures observed in the Maldive islands, this reef

Geotourism highlights of Gotland 75

Bronze Age cairn at Uggarderojr. type is called ‘faro’. On Gotland, such structures are known only from the uppermost Sundre Formation. The reefs are composed of dense stromatoporoid and crinoidal limestones, normally with a fine-grained infill (matrix). Occasionally, solenoporaceen algae are present. The reef rocks alternate with crinoidal lime- stones, and coarse, partly conglomeratic limestones. Interior areas of the faros formed lagoons, which were presumably filled with soft sediments. Conspicuous vertical fissures, up to 0.5 m wide, cut radially and concentrically through these reef rings. These so called neptunian dykes have been repeatedly opened and refilled with sediment. The faros were situated on the south-eastern margin of an extended stromat- oporoid reef platform. During rising sea level, they grew predominantly in a south-easterly direction, and because of their increasing size and weight fissures were opened, and then filled repeatedly with sedi- mentary material.

Along the gravel road leading to the north, there is a bay named Skvalpvik, which has a fine sandy beach. And slightly further on is another sea stack area; Hammarshagehällar.

South of the sea stack area at Holmhällar there is an old fishing base, where the stone huts have sand- stone-slab roofing, typical of southern Gotland build- ings. Fishing was an important supplement to the diet of farmers in the coastal parishes, where the soil is thin and poor. Most farmers owned a hut at a coastal fishing base. Baltic herring was the main catch.

There are also sea stacks and caves on the islet of , a bird sanctuary just off Holmhällar, where gulls and terns breed in spring and early sum- mer. Access is prohibited between 15th March and 30th June.

76 Fostering Geotourism on the Central Baltic Islands Holmhällar rauks. Photo: T. Bauert.

Geotourism highlights of Gotland 77 Husrygg and Hoburgen and a good number of fossils. However, Hoburgen is not predominantly a fossil locality, but is mainly The best known scenic route with some of the fin- worth a visit to see its sedimentary rocks and the est views on Gotland is along the road that winds information that the area provides of the most recent between the sea in the west and the ridge-like lime- history of the Silurian on Gotland. stone hill of Hysrygg in the east, far down in the south of the island at Storsudret. Husrygg is gently rounded The cliffs reach a height of 30 metres. They are built by the waves of the Ancylus Lake and Littorina Sea. up from the three youngest stratigraphical units of The thin soil cover and grazing over a long time have Gotland: Burgsvik, Hamra and Sundre formations. created an alvar with low vegetation. Here breckland The second hill from the south descends abruptly to thyme, Vincetoxicum, Euphrasia and salad burnet the beach, with quite a steep section. On the beach, grow in profusion. If you have chosen to visit Gotland at the water’s edge, especially at low tide, the upper in the second half of April or in the beginning of May, part of the Burgsvik Formation is clearly visible, con- you should climb up the slopes to admire the bloom- sisting of sandstone and oolite. Oolite means ’fish roe ing pheasant’s eye (Adonis vernalis), a relict from the stone’, and the name refers to the similarity between Warm Period. In all the , it occurs the small round spherical calcareous particles that only here, on Stora Karlsö, and on Öland. Otherwise make up the rock, and fish roe. Calcareous particles, it grows on the steppelands of south-. ooids, are of sand-grain size, 0.06 – 2 mm, and have The road leads south to Hoburgen, an area consist- been formed by the deposition of coatings of calcium ing of five hills of reef limestone on the south-west- carbonate around tiny fragments that were rolled ernmost peninsular of the island. Tourists flock to this around in very shallow, warm water. Ooliths made spot, mainly to see the remarkable sea stacks, such up of larger fragments are called pisoliths, meaning as the famous Hoburgsgubben (Old Man of Hobur- ‘pea stones’. gen) and the deep caves, the most famous of which In the cliff section, the sequence of layers is easy is Hoburgsgubbens sängkammare (the Old Man’s to follow. At the bottom is the Burgsvik Sandstone. chamber). According to folklore, a giant lived in this This is then succeeded gradually by the fossiliferous cave. He had moved to Gotland with all his treasures Burgsvik Oolite, in which cross-bedding can be seen. and with the stolen church bell from Kisa church in The oolite becomes increasingly pisolithic (the grains Östergötland on the Swedish mainland, because he become coarser) higher up. The Burgsvik Formation, disapproved of the building of a church in his neigh- no more than 1.5 metres at this point, is overlain by a bourhood. marly and highly fossiliferous limestone belonging to The sea stacks and caves were sculpted by waves the Hamra Formation. Some of the sediment is made of the Ancylus Lake 8000 years ago. The undulating up of conglomeratic calcareous algae, derived from raised beaches along the shingle shores were thrown the calcareous algae Rothpletzella. Both the oolites up by storms, and the characteristic wave pattern has and the calcareous algae indicate a very shallow been formed as the land rose slowly from the sea. depositional environment. The rest of the limestone is

Hoburgen exhibits interesting bedrock geology, with Husrygg scenery at sunset (top). Hoburgsgubben – a large variety of rock types, sedimentation structures, the Old Man of Hoburgen. Photos: T. Bauert.

78 Fostering Geotourism on the Central Baltic Islands Geotourism highlights of Gotland 79 mainly fragmental. The Hamra Formation at this point ries between the road and the sea, often with large is about 20 metres thick. piles of waste stone lying on the coastal side of the The upper part of the cliff consists of stratified and quarries. However, in Kettelviken bay there is an easy reef limestones belonging to the very youngest for- accessible natural coastal section cutting through the mation on Gotland, the Sundre Formation, with a sediments, which belong to the Burgsvik Formation, thickness at this point of about 8 metres. Most of one of the younger formations on the island. The sedi- the rocks are reddish limestones consisting almost ments are thinly and thickly bedded, light grey, fine- entirely of crinoidal remains that have fallen down grained sandstones, partly interbedded with bands from the nearby reef and now form a coarse frag- of argillaceous rock. In the uppermost part of the mental limestone. This has been quarried under the sequence there are oolitic and oncolitic (calcareous name of Hoburg Marble, and used for decoration and algae) limestones. sculptures, predominantly in churches in the south of Sandstones on Gotland occur essentially only along a Gotland. A gaping hole in the southernmost and larg- small belt running from Grötlingbo in a south-easterly est hill is a heritage from a long period of quarrying of direction along the west coast of Storsudret down to Hoburg Marble. In large boulders of stone debris, you Hoburgen. The sandstones are made of quartz grains can study the beautiful red limestone whose fractures cemented by calcium carbonate; that is, the pore glisten in the sun. The quarrying, which was carried spaces between the sand grains have been filled with out since the Medieval Period, was abandoned long calcite precipitated from water trickling through the ago, when the quarry had been depleted of its best sediment. Since calcite is easily soluble and the stone stones. The name ‘marble’ is of course erroneous, but becomes porous, the sandstone rock crumbles rather it has been used commercially both for this and for easily. This also makes it easy to work for building other crinoidal limestones, such as Karlsö Marble. and sculptures. Furthermore, it occurs in easily-quar- By you ascending the scree slope and walking up the ried, homogenous layers. In air-polluted , such hill path, you will see the large reefs at close range. sandstone buildings and sculptures are unfortunately These have been subjected to detailed scientific study, decomposing at an alarming rate. and give their name to a ’Hoburgen reef type’, which The sandstone was deposited as a near-shore sedi- is characterized firstly by its size of about 100 m2, ment. Ripples are common, as well as other sedi- secondly by its content of many different species, and mentary structures indicating a shallow environment. thirdly by the predominance of stromatoporoids, cor- Finer bedding, sitting at a low angle across the hori- als and calcareous algae. zontal beds, is also preserved in the section. This is known as cross-bedding, which indicates a rapid dep- osition of sand, either in a tidal environment or during Kettelvik a storm. Other, somewhat larger structures include Along Storsudret – the western coast of southern- concave beds, indicating partial collapse of the sedi- most Gotland – there are low cliffs formed mainly ments before they became lithified, possibly due to of sandstone. Because the sandstone was quarried minor earthquakes. Towards the end of the Silurian in the past, most exposures are in abandoned quar- Period, when these sediments were formed, the colli-

80 Fostering Geotourism on the Central Baltic Islands sion between ‘our’ continent and Laurentia was draw- and imprints of resting animals, all documenting the ing to a close. The resulting high mountain range, of activities of a bottom-living fauna in this environ- which the Norwegian-Swedish mountain chain is a ment. remaining part, immediately began to erode, and pro- vided enormous volumes of sediment in the form of clay, sand and gravel. Volcanic eruptions and move- Kettelviken Sandstone Museum ments in the crust of the earth were also associated Along the beautiful western coastal road down to with these events. The boundary between the sand- Hoburgen, there is a series of small stone quarries, stones and the overlying limestones represents a time between the road and the sea. Here, sandstone has when sea level began to rise again. been quarried since the 11th century. The stone was Oolite means ‘fish roe stone’, and the name alludes used for baptismal fonts, and for building and orna- to the similarity between the small round spherical mental stones, which were exported to the mainland calcareous particles that make up the rock, and fish and the continent. Even grinding stones and whet- roe. Calcareous particles (ooids) are of sand-grain stones have been, and still are, an important product size, formed by the deposition of coatings of calcium of sandstone. carbonate around tiny fragments that rolled around in A museum exhibiting the history of stone quarry- very shallow, warm water. ing and Limeworks industry has been set up in one Oncolitic, or algal limestones consist mainly of irreg- of the old abandoned quarries just south of the bay ular calcareous nodules, a few centimetres in size. In of Kettelvik. The last stonemason worked here until cross-section each nodule can be seen to be made up the 1980s. Grinding stones were produced. In the of thin, spherical layers of calcium carbonate coating a museum there are displays that show how the quar- core of shelly fragments. These calcareous nodules were rying was done, and how the stone was processed. formed by calcite-precipitating algae in shallow water. Tools, grinders and a wind-power-driven water pump are still preserved. Grinding stone history and stone Fossils are relatively scarce in the sandstone. On hori- workers life is portrayed in the indoor exhibition. You zons in the oolitic upper part of the section, however, can also try to cut sandstone using traditional tools. there are accumulations of shells from the bivalve Pteronitella, together with numerous other fragmen- The sandstone was mined in opencast workings tal fossils. Parts of the large trilobite Homalonotus located alongside the beach. The natural low coastal occur in the sandstone, and with a certain degree of cliffs, where sandstone layers were accessible from stubbornness, time and a stroke of luck, it might be the side, were used initially, and then the stone was possible to find parts of fishes such as acanthodians gradually quarried towards the inland. Waste stone and ostracoderms. Otherwise, in the Burgsvik Sand- was thrown in heaps on the seaward side. The sand- stone, the richest finds of spores from the oldest ter- stone was thickly bedded, with thin clay layers in restrial plants can be made. Trace fossils in the form between and with vertical cracks cutting the stone. of infilled tunnels of burrowing organisms, probably These cracks and clay layers were a precondition for bristle worms, are common in the sandstone. It is also breaking the stone easily, with the methods that were possible to find various kinds of traces, grazing tracks available at that time.

Geotourism highlights of Gotland 81 82 Fostering Geotourism on the Central Baltic Islands

Kettelviken Sandstone Museum. Geotourism highlights of Gotland 83 Stora Karlsö and Lilla Karlsö glacier left the area. Subsequent uplift then led to the origin of the island. On higher areas, such as The small islands of Lilla Karlsö and Stora Karlsö, off Raisu Haid and Marmorberget, loose weathered rock the south-western coast of Gotland, are clearly visible deposits are almost completely washed away. Intense from the coast of Eksta. The islands are south-westerly wave action has also carved out a number of caves extensions of the reef complex that runs from north- in the cliff walls. The 25 metre deep Stora Förvar, eastern Gotland, across the Klinte area and out into together with Jungfruhålet and Korphålet at a depth the sea. of 12 metres, are caves formed by waves of the Ancy- Stora Karlsö is the largest and furthermost island, lus Lake. Well-formed sea stacks are preserved at the 6 km from the coast of Gotland. It has an area of less beach called Svarthällar on the south-eastern coast. than 2.5 km2. The bedrock comprises mainly hard The waves have also thrown up shingle in unusually reef limestone and bedded limestone belonging strati- well-developed beach ridges. graphically to the Slite Group. Along the west coast Until the late 17th century sheep grazed the entire there is a fossiliferous marlstone unit. island all year around and the original forest had A horseshoe-shaped plateau dominates the island, long since given way to a grazing-resistant vegeta- forming a slightly arched and somewhat hilly surface tion. After 1884, when grazing was stopped, decidu- because of the reefs in the bed rock. The highest point, ous trees and other lush vegetation began to regain Roisu Haid, is 52 metres above sea level, located on ground. Today, a part of the island is again pasture- the eastern side, while Marmorberget on the plateau’s land. western section is 45 metres above sea level. Between Stora Karlsö is known for its rich flora. In late April these points, in the shallow hollow of the plateau, is and into mid-May pheasant’s eye (Adonis vernalis), a the plain of Norderslätt, bounded by the steep cliff of heat-loving steppe plant, blooms commonly. Other­ Norderhamnsberget to the west and Austerberget in wise in Scandinavia it is found only along Husrygg the east. A beach plain, Suderslätt, covered with sea at Hoburgen and on Öland. The elder-flowered and ridges of shingle, spreads to the south. early purple orchids show displays of colours a few In the west, north and north-east, the plateau is weeks earlier. Globularia vulgaris, Anemone sylves- bounded by steep, 10-30 metres high coastal cliffs. tris, goldilocks aster, Mulgedium quercinum and Rocks and boulders form large scree areas on the Artemisia rupestris are other heat-loving plants that foreshore below. The plateau is criss-crossed with previously had a wider distribution. Stora and Lilla cracks in the bedrock caused by movements in the Karlsö have Sweden’s only bird cliffs, on which guil- crust. On the cliff slopes, these are often developed lemots and razorbills nest. as caves and gorges. At the south-western part of Mar- Lilla Karlsö is just over 3 km off the coast of Gotland morberget the cracks have been subjected to chemi- and 4.5 km from Stora Karlsö. It is 1.6 km2 in area, cal weathering and a distinctly flat karst landscape is dominated by an almost circular plateau whose high- formed. est point is 66 metres above sea level. The plateau is Like the rest of Gotland, Stora Karlsö was completely bounded on the north and south by beach plains, but below the water surface at the time when the inland in the west and east are steep cliffs that drop almost

84 Fostering Geotourism on the Central Baltic Islands straight down to the sea. At various levels in the cliffs Like Stora Karlsö, Lilla Karlsö is however, best known the sea has hollowed out some 25 caves, of which a for its bird life. Large numbers of guillemots and few are 30 metres deep. Some sea stacks are present razorbills breed on the steep cliffs. Other typical birds along parts of the coast. are herring gull, lesser black-backed gull, great black- The vegetation of Lilla Karlsö is affected by intensive backed gull, eider, velvet scoter, northern wheatear sheep grazing, which has been maintained on the and rock pipit. A newcomer to the island’s fauna is island for hundreds, perhaps thousands of years, and the great cormorant, which began nesting here in most of the island is barren of trees and shrubs. Only 1992, since when numbers have risen sharply. in the scree above Suderslätt is there a sparse grove of Both islands are nature reserves and have large bird several hundred year old ashes, oaks and elms. Lilla sanctuaries. It is also strictly forbidden to collect Karlsö is now grazed by Gutefår, an ancient Gotland fossils. Day visitors during the nesting season may breed of sheep in which both rams and ewes have not walk freely around the islands, but must be in horns. the company of the knowledgeable guides. There is The flora of Lilla Karsö is dominated by pasture- accommodation on both islands. Between May and dwelling species, such as sheep’s fescue, meadow oat August there is daily boat transport from Klintehamn grass, soft-brome, common rock-rose, Vincetoxicum, to Stora Karlsö. From Djupvik fishing village, about breckland thyme, lady’s bedstraw, rock wormwood, 15 km south of Klintehamn, there are daily to wild marjoram and spiked speedwell. Lilla Karlsö. Stora Karlsö. Photo: T. Bauert.

Geotourism highlights of Gotland 85 86 Fostering Geotourism on the Central Baltic Islands Stora Karlsö scenery. Photo: T. Bauert. Geotourism highlights of Gotland 87 Langhammarshammar Digerhuvud Avanäset Tunguhuvud Gamlahamn

Bläse FÅRÖ

Fårö- Sigsarve sund Ireviken Bungenäs Lickershamn Lergrav Lärbro

Lummelunda Kyllaj Furillen Slite

Tingstäde Kallgateburgs St. Olofsholm

Korpklint Hejnum hällar

VISBY Gothemhammar Högklint Rövar Liljas håla

Roma

Grogarnshuvud

GOTLAND Kuppen

Klintehamn Folhammar Gannarve Lilla Karlsö Stånga

Stora Karlsö

Hemse

Havdhem Uggarderojr

Burgsvik Faludden geotourism sites described in the text geotourism sites mentioned in the text Kettelvik 0 5 10 km Husrygg Holmhällar Hoburgen

ISBN 978-9985-9973-4-5

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